CZERWIEC - WRZESIEŃ · face. The mechanical properties of the coating and substrate and adhesion...

Numer 56-57Rok IXISSN 1429-7248

CZERWIEC - WRZESIEŃ 2006

WYDAWCA:

PolskieStowarzyszenie Biomateriałóww Krakowie

KOMITETREDAKCYJNY:

Redaktor naczelnyStanisław BłażewiczSekretarz redakcji,Skład komputerowyAugustyn Powroźnik

RADANAUKOWA:

Jan RyszardDąbrowski

Jan Chłopek

Tadeusz Cieślik

Monika Gierzyńska-Dolna

Andrzej Górecki

Wojciech Maria Kuś

Jan Marciniak

Stanisław Mazurkiewicz

Stanisław Mitura

Roman Pampuch

Bogna Pogorzelska-Stronczak

ADRES REDAKCJI:Akademia Górniczo-Hutniczaal. Mickiewicza 30/A-330-059 Kraków

Nakład: 200 egz.Wydawnictwo NaukoweAKAPITe-mail: [email protected]

E N G I N E E R I N G O F B I O M A T E R I A L SC Z A S O P I S M O P O L S K I E G O S T O W A R Z Y S Z E N I A B I O M A T E R I A Ł Ó W

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MODYFIKACJA POWIERZCHNI TYTANU POWŁOKĄ DIAMENTOPODOBNĄ 1M. BIEL GOŁASKA, I. KALEMBA, J. RADZIKOWSKA, M. WARMUZEK, B. RAJCHEL, W. RAKOWSKI

PULSED CATHODIC ARC PLASMA TECHNOLOGY DEPOSITION OF THROMBORESISTANT NANOSTRUCTURAL CARBON COATING ON COMPONENTS OF ARTIFICIAL HEART VALVES 12E.I. TOCHITSKY

THE CHLORINATED SYNTHETIC DIAMOND SURFACE INTERACTION WITH C-NUCLEOPHILES 16V.V. KOROLKOV, B.N. TARASEVICH, I.I. KULAKOVA, G.V. LISICHKIN

GROWTH OF CELLS ON CARBON COATINGS MANUFACTURED IN NEW MW/RF REACTOR 19I. ŠUBRTOVÁ, L. GRAUSOVÁ, L. BAČÁKOVÁ, W. KACZOROWSKI

ELECTRIC POTENTIAL OF BIOMATERIALS COATED WITH DIELECTRIC CARBON LAYER AND NON-COATED IN WATER AND SERUM 21S. URBAŃSKI, P. NIEDZIELSKI, S. MITURA, T. WIERZCHOŃ, A. SOKOŁOWSKA

CARBON FIBRE-BASED POSTS WITH CEMENTIT UNIVERSAL RESIN CEMENTATION SYSTEM AS A MATERIAL FOR RESTORATION OF ENDODONTICALLY COMPROMISED TEETH – SEM EVALUATION OF SEALING 24K. BANASZEK, L. KLIMEK

MODIFYING ELECTROPHYSICAL PROPERTIES OF SI-CBN INTERFACE BY INTRODUCTION OF ULTRATHIN DIELECTRIC LAYER 27P. FIREK, R. MROCZYŃSKI, J. SZMIDT, R.B. BECK, A. WERBOWY

THE EFFECT OF PARTICLES, INCLUDING NANOPARTICLES, ON MACRO PHAGES IN VITRO AND IN VIVO 29P.A. REVELL, H. ALTAF, T. MCFARLANE, D. BOCIAGA, K. MITURA

CONTENTS

MODIFICATION OF THE TITANIUM SURFACE WITH A DIAMOND-LIKE CARBON COATING APPLICATIONS 1M. BIEL GOŁASKA, I. KALEMBA, J. RADZIKOWSKA, M. WARMUZEK, B. RAJCHEL, W.RAKOWSKI

PULSED CATHODIC ARC PLASMA TECHNOLOGY DEPOSITION OF THROMBORESISTANT NANOSTRUCTURAL CARBON COATING ON COMPONENTS OF ARTIFICIAL HEART VALVES 12E.I. TOCHITSKY

THE CHLORINATED SYNTHETIC DIAMOND SURFACE INTERACTION WITH C-NUCLEOPHILES 16V.V. KOROLKOV, B.N. TARASEVICH, I.I. KULAKOVA, G.V. LISICHKIN

GROWTH OF CELLS ON CARBON COATINGS MANUFACTURED IN NEW MW/RF REACTOR 19I. ŠUBRTOVÁ, L. GRAUSOVÁ, L. BAČÁKOVÁ, W. KACZOROWSKI

ELECTRIC POTENTIAL OF BIOMATERIALS COATED WITH DIELECTRIC CARBON LAYER AND NON-COATED IN WATER AND SERUM 21S.URBAŃSKI, P.NIEDZIELSKI, S.MITURA, T.WIERZCHOŃ, A.SOKOŁOWSKA

CARBON FIBRE-BASED POSTS WITH CEMENTIT UNIVERSAL RESIN CEMENTATION SYSTEM AS A MATERIAL FOR RESTORATION OF ENDODONTICALLY COMPROMISED TEETH – SEM EVALUATION OF SEALING 24K. BANASZEK, L.KLIMEK

MODIFYING ELECTROPHYSICAL PROPERTIES OF SI-CBN INTERFACE BY INTRODUCTION OF ULTRATHIN DIELECTRIC LAYER 27P. FIREK, R. MROCZYŃSKI, J.SZMIDT, R.B. BECK, A. WERBOWY

THE EFFECT OF PARTICLES, INCLUDING NANOPARTICLES, ON MACROPHAGES IN VITRO AND IN VIVO 29P.A REVELL, H. ALTAF, T.MCFARLANE, D. BOCIAGA, K. MITURA


STRESZCZANE W APPLIED MECHANICS REVIEWS

ABSTRACTED IN APPLIED MECHANICS REVIEWS

WYDANIE DOFINANSOWANE PRZEZ MINISTRA NAUKI I SZKOLNICTWA WYŻSZEGO

EDITION FINANCED BY THE MINISTER OF SCIENCE AND HIGHER EDUCATION

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THE INFLUENCE OF NANOCRYSTALLINE DIAMOND LAYERS OBTAINED BY MW/RF PECVD METHOD ON SURFACE PROPERTIES OF AISI 316 L STEEL 31T. BLASZCZYK, B. BURNAT, H. SCHOLL,P. NIEDZIELSKI, W. KACZOROWSKI

CORROSIVE FEATURES OF TI WITH NANO-CRYSTALLINE DIAMOND LAYERS OBTAINED BY MEANS RADIO FREQUENCY AND MICROWAVE / RADIO FREQUENCY PLASMA CHEMICAL VAPOR DEPOSITION METHODS 34B. BURNAT, W. KACZOROWSKI, G. BOGUSLAWSKI, T. BLASZCZYK, H. SCHOLL

PROPERTIES OF NITI - SHAPE MEMORY ALLOY AFTER MODIFICATION BY RF PCVD METHOD 37M. CZERNIAK-RECZULSKA, P. COUVRAT, J. GRABACZYK, P. NIEDZIELSKI

BIOMATERIAŁY W LECZENIU POURAZOWYCH UBYTKÓW NERWÓW OBWODOWYCH –PRZEGLĄD METOD I MATERIAŁÓW 40D. SZAREK, W. JARMUNDOWICZ, A. FRĄCZEK, S. BŁAŻEWICZ

PROJEKTOWANIE WŁASNOŚCI RESORBOWALNYCH, METALICZNYCH IMPLANTÓW KOSTNYCH – ZASTOSOWANIE W WARUNKACH IN VIVO 54F.W. BACH, R. KUCHARSKI, D. BORMANN, D. BESDO, S. BESDO, C. HACKENBROICH, F. THOREY, A. MEYER-LINDENBERG

MAGNEZOWE STRUKTURY HYBRYDOWE W ZASTOSOWANIU NA LECZENIE UBYTKÓW KOSTNYCH 58F.W. BACH, R. KUCHARSKI, D. BORMANN

THE INFLUENCE OF NANOCRYSTALLINE DIAMOND LAYERS OBTAINED BY MW/RF PECVD METHOD ON SURFACE PROPERTIES OF AISI 316 L STEEL 31T. BLASZCZYK, B. BURNAT, H. SCHOLL,P. NIEDZIELSKI, W. KACZOROWSKI

CORROSIVE FEATURES OF TI WITH NANO-CRYSTALLINE DIAMOND LAYERS OBTAINED BY MEANS RADIO FREQUENCY AND MICROWAVE / RADIO FREQUENCY PLASMA CHEMICAL VAPOR DEPOSITION METHODS 34B. BURNAT, W. KACZOROWSKI, G. BOGUSLAWSKI, T. BLASZCZYK, H. SCHOLL

PROPERTIES OF NITI - SHAPE MEMORY ALLOY AFTER MODIFICATION BY RF PCVD METHOD 37M. CZERNIAK-RECZULSKA, P. COUVRAT, J. GRABACZYK, P. NIEDZIELSKI

BIOMATERIALS IN THE TREATMENT OF PERIPHERAL NERVE INJURIES –AN OVERVIEW OF METHODS AND MATERIALS 40D. SZAREK, W. JARMUNDOWICZ, A. FRĄCZEK, S. BŁAŻEWICZ

DESIGN OF RESORPTION PROPERTIES OF THE METAL BONE IMPLANTS –APPLICATION IN VIVO 54F.W. BACH, R. KUCHARSKI, D. BORMANN, D. BESDO, S. BESDO, C. HACKENBROICH, F. THOREY, A. MEYER-LINDENBERG

MAGNESIUM COMPOUND STRUCTURES FOR THE TREATMENT OF BONE DEFECTS 58F.W. BACH, R. KUCHARSKI, D. BORMANN

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MODYFIKACJA POWIERZCHNITYTANU POW£OK¥DIAMENTOPODOBN¥

BIEL GO£ASKA MARTA*, KALEMBA IZABELA**,RADZIKOWSKA JANINA*, WARMUZEK MA£GORZATA*,RAJCHEL BOGUS£AW***, RAKOWSKI WIES£AW**

*INSTYTUT ODLEWNICTWA, KRAKÓW

**AGH, WYDZIA£ IN¯YNIERII MECHANICZNEJ I ROBOTYKI, KRAKÓW

***INSTYTUT FIZYKI J¥DROWEJ PAN, KRAKÓW

E-MAIL: [email protected]

Streszczenie

Artyku³ dotyczy uszlachetniania powierzchni tyta-nu pow³ok¹ diamentopodobn¹ w celu zwiêkszeniajego biotolerancji w organimie ludzkim.Na powierzchni próbek z tytanu wytworzono ochron-n¹ warstwê diamentopodobn¹, stosuj¹c metodê im-plantacji jonowej. Dokonano oceny jej w³asnoci me-chanicznych oraz adhezji do pod³o¿a metalowego.Scharakteryzowano w³asnoci u¿ytkowe implantówmetalowych oraz stawiane im wymagania.Omówiono metodê jonow¹ IBAD formowania pow³okwêglowych na materia³ach metalowych, jak równie¿metodykê badañ wytrzyma³oci, mikrotwardoci,szczelnoci i adhezji pow³ok do pod³o¿a metalowego.Przedstawiono wyniki badañ mechanicznych i adhe-zji do pod³o¿a oraz zamieszczono sugestie odnoniekierunków dalszych badañ.

Slowa kluczowe: implanty metalowe, tytan, po-w³oka diamentopodobna, implantacja jonów, adhezja,mikrostruktura, w³aciwoci mechaniczne.

[In¿ynieria Biomateria³ów, 56-57,(2006),1-11]

WstêpPróby wykorzystania obcych materia³ów w organimie

ludzkim siêgaj¹ praktycznie pocz¹tków medycyny. W tymcelu stosowane by³y ró¿ne materia³y: drewno, koci zwie-rz¹t oraz metale szlachetne, takie jak z³oto i srebro. W la-tach czterdziestych XX wieku przeprowadzono pierwszepróby zastosowania tytanu i jego stopów w chirurgii kost-nej. O ich przydatnoci zdecydowa³a bardzo dobra odpor-noæ korozyjna w rodowisku tkankowym. Nale¿y podkre-liæ, ¿e maj¹ one mniejszy ciê¿ar w³aciwy w porównaniuze stopami na osnowie ¿elaza i kobaltu, co stanowi wa¿n¹zaletê tworzywa wykorzystywanego na endoprotezy stawo-we. Stopy tytanu znalaz³y równie¿ zastosowanie w protety-ce stomatologicznej oraz kardiologii [1, 2].Tytan i jego stopy znajduj¹ szerokie zastosowanie jakowszczepy czasowe w postaci prêtów, gwodzi, grotów, dru-tów, wkrêtów i p³ytek w rekonstrukcji z³amañ koci oraz jakowszczepy trwa³e w postaci protez stawów lub ich czêci,sztucznych zastawek serca, a tak¿e w wielu wyrobach, ta-kich jak stymulatory serca.Niekiedy stosowane nazwy implantów nawi¹zuj¹ do ichkonkretnego umiejscowienia. Mo¿na tu zaliczyæ ró¿ne ro-dzaje implantów pokazane na RYS. 1-7:- implant ortopedyczny - stosowany by wspomóc koæ,chrz¹stkê, wiêzad³a, ciêgna lub powi¹zane z nimi tkanki,albo zastêpuj¹cy lub uzupe³niaj¹cy tymczasowo brak nasta³e tkanki (RYS. 5,6,7),- implant czaszkowo-twarzowy - stosowany w obszarzeczaszkowo-twarzowym wy³¹czaj¹c obszar jamy ustnej, któryma na celu poprawienie lub zast¹pienie okrelonych tka-

MODIFICATION OF THE TITANIUMSURFACE WITH A DIAMOND-LIKECARBON COATING

BIEL GO£ASKA MARTA*, KALEMBA IZABELA**,RADZIKOWSKA JANINA*, WARMUZEK MA£GORZATA*,RAJCHEL BOGUS£AW***, RAKOWSKI WIES£AW**

*FOUNDRY RESEARCH INSTITUTE, CRACOW, POLAND

**AGH-USC, FACULTY OF MECHANICAL ENGINEERING AND

ROBOTICS, CRACOW, POLAND

***INSTITUTE OF NUCLEAR PHYSICS, POLISH ACADEMY OF SCIENCE

CRACOW, POLAND

[email protected]

Abstract

Modification of the surface of titanium alloy biomate-rial with the diamond--like carbon coating (DLC) inorder to increase its biocompability in the human or-ganism, its hardness and wear resistance wereanalyzed.The diamond-like carbon coatings were formed on thetitanium specimens, then their adhesion to the metalsubstrate was evaluated. Ion Beam Assisted Deposi-tion method was used for improving the titanium sur-face. The mechanical properties of the coating andsubstrate and adhesion to the base metal were evalu-ated.

Morphology of titanium and the diamond-like car-bon films were examined under the Light and Scan-ning Microscope. The microscopic examinations re-vealed satisfying structural homogeneity on the coatedsurface.The results of microstructural and mechanical testsas well as of those concerning the adhesion to thebase are given. The utilization properties of metalimplants and the requirements which are imposed ontothem were characteristed.

Keywords: metal implants, titanium, diamond-likecarbon coating (DLC), ion implantation, adhesion,

[Engineering of Biomaterials, 56-57,(2006),1-11]

IntroductionAttempts at introducing foreign materials to the human

organism practically date back to the beginnings of medi-cine. To this end various materials, such as wood, animalbones and precious metals were used. In forties of the 20thcentury, first attempts at the application of titanium and itsalloys in bone surgery were made. Very good corrosion re-sistance in the medium of the tissues decided about theirutility. It should be stressed that, compared with iron- andcobalt-based alloys, they have lower mass density which isan important advantage of the material used forendoprostheses of joints. Titanium alloys also found appli-cation in dental protectics and in cardiology [1,2].Titanium and its alloys find extensive application as tempo-rary implants in the form of bars, nails, wires, darts, screwsand plates for the reconstruction of fractured bones, and asdurable implants of the joint endoprostheses or parts of thoseendoprostheses, artificial heart valves and numerous otherproducts, e.g. heart pacemakers. Sometimes the names of the implants refer to their specificlocation. Among various implants, the following ones canbe distinguished. (FIGs.1-7)· orthopaedic implants - used to support bones, gristles,

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ligaments, tendons or tissues connected with them, or toreplace or make up for a permanent lack of the tissues (FIGs.5,6,7);· skull-facial implants - used in the skull-facial area ex-cluding oral cavity, which should improve or replace somespecific hard or soft tissues, except the brain, eyes and in-ner ear (FIGs.2,3);- dental implants - used in the oral cavity to make up forthe lacking teeth (FIG. 4).Various usable forms of implants are made from titaniumbiomaterials (FIG.1) [3].There is still one problem not solved to the very end, namelywhether titanium is completely safe and whether it can gettransformed in the human tissues and with what possibleconsequences for the recipient [4].Metals and their alloys used in implantation should be char-acterised by the following features [5, 6, 7]:- high corrosion resistance,- biocompability (atoxicity),- required chemical composition and fine-grained structure,- suitable strength,- required surface condition,- no tendency to formation of thrombi,- suitable electric and magnetic properties,- susceptibility to mechanical working,- reasonable manufacturing costs.Biocompability (biological comformity) is one of the mostimportant characteristic features of implants. It is connectedwith the implant susceptibility to corrosion or biodegrada-tion, and the related predisposition to the initiation of toxicor allergic reactions and also with tissues response to thepresence of a foreign body. The most important influenceon the degree of biological compatibility have corrosionresistance, electric properties, and abrasion wear resistance.To protect metal implants against corrosion, their surface iscovered with a fine layer. The structure and properties ofthe top layer decide to a large extent on the behaviour ofproducts during their performance.The task for the nearest future of this field of science iscreating a background against which the processes ena-bling manufacture of the surface layers characterised bysome specific properties tailored to the individual require-ments can be successfully developed.Carbon as a main component in the structure of the humanbody tissues is an ideal material for implants used in medi-cine. All allotropic forms of carbon meet the requirementsimposed onto implants. Diamond (FIG.8a) is one of the allotropic forms of carbon.It possesses a number of valuable properties, which makeit useful in many fields, especially in medicine. It is charac-terised by very high durability and corrosion resistance, ischemically inactive, and has very high thermal conductivity.It is, moreover, biocompatible. Investigations aiming at theelaboration of various methods of the synthesis of diamondparticles and diamond layers have been carrying out formore than 50 years. In the last twenty years, ionic tech-niques were applied to fabricate diamond or diamond-likecarbon layers. One of the ionic techniques was applied tothe synthesis of nanocrystalline carbon layers.The proper-ties of carbon layers depend on the method of their fabri-cation. There are problems with unification of the descrip-tion of the layers with individual features. Generally, de-pending on the structure, the produced carbon material canbe divided into the following main groups [8].Diamond - containing diamond layers and layers ofpolycrystalline diamond, composed of atoms with hybridforms of the ssp3 type electrons.Nanocrystalline, tetrahedral or amorphous diamond -are the terms used to stress the fact that although almost

nek twardych lub miêkkich, z wyj¹tkiem mózgu, oczu i uchawewnêtrznego (RYS. 2, 3),- implant dentystyczny - to rodzaj implantu ustnego sto-sowany do uzupe³nienia ubytku zêba (RYS. 4).Z biomateria³ów tytanowych wytwarzane s¹ ró¿ne u¿ytko-we postacie implantów (RYS. 1) [3].Pozostaje jednak nierozwi¹zany do koñca problem, a mia-nowicie: czy tytan jest ca³kowicie bezpieczny, czy te¿ zmienisiê w rodowisku tkanek i z jakimi ewentualnymi konse-kwencjami dla biorcy [4].Metale i ich stopy stosowane w implantacji powinny cha-rakteryzowaæ siê nastêpuj¹cymi cechami [5, 6, 7]:- dobr¹ odpornoci¹ na korozjê,- biotolerancj¹ (nietoksycznoæ),- odpowiednim sk³adem chemicznym i drobnoziarnist¹ struk-tur¹,- dobr¹ wytrzyma³oci¹,- okrelonym stanem powierzchni,- brakiem tendencji do tworzenia zakrzepów,- posiadaniem odpowiednich w³aciwoci elektrycznych orazmagnetycznych,- podatnoci¹ na obróbkê mechaniczn¹.Biotolerancja (biokompatybilnoæ, zgodnoæ biologiczna)jest jedn¹ z najwa¿niejszych cech implantów. Zwi¹zana jestona z podatnoci¹ wszczepu na korozjê lub biodegradacj¹,a co z tym siê wi¹¿e - sk³onnoci¹ do inicjowania reakcjitoksycznych i alergicznych, a tak¿e mechaniczn¹ reakcj¹tkanek na obce cia³o. Najwiêkszy wp³yw na stopieñ zgod-noci biologicznej implantu maj¹ odpornoæ na korozjê,odpowiednie w³aciwoci elektryczne oraz odpornoæ nazu¿ycie cierne.W celu zabezpieczenia implantów metalowych przez koro-zj¹, ich powierzchniê pokrywa siê cienk¹ warstw¹ wierzch-ni¹. Struktura i w³aciwoci warstwy wierzchniej w du¿ymstopniu decyduj¹ o zachowaniu siê wyrobów w czasie icheksploatacji.Zatem zadaniem na najbli¿sz¹ przysz³oæ jest stworzeniepodstaw umo¿liwiaj¹cych projektowanie procesów wytwa-rzania warstw powierzchniowych o okrelonych w³aciwo-ciach, stosownie do wymagañ.Wêgiel jako podstawowy sk³adnik struktury tkanek cz³owie-ka jest idealnym materia³em stanowi¹cym element implan-tów stosowanych w medycynie. Wszystkie odmiany alotro-powe wêgla spe³niaj¹ wymagania stawiane wszczepom.Diament (RYS. 8a) jest jedn¹ z alotropowych postaci wê-gla. Charakteryzuje siê cennymi w³aciwociami, które czy-ni¹ go przydatnym w wielu dziedzinach, a szczególnie wmedycynie. Diament odznacza siê bardzo du¿¹ trwa³oci¹,odpornoci¹ na korozjê, jest chemicznie nieaktywny, mabardzo du¿a przewodnoæ ciepln¹, jest materia³em biozgod-nym. Od ponad piêædziesiêciu lat prowadzone s¹ badaniamaj¹ce na celu opracowanie metod syntezy cz¹stek dia-mentowych i warstw diamentowych. W ci¹gu ostatnich dwu-dziestu lat do wytwarzania warstw diamentowych oraz dia-mentopodobnych zastosowano techniki jonowe. Jedn¹ ztechnik jonowych zastosowano do zsyntetyzowania nano-krystalicznych warstw wêglowych. W³aciwoci warstwwêglowych zale¿¹ od sposobu ich wytwarzania. Stwarza toproblemy z ujednoliceniem opisu warstw o poszczególnychcechach. Generalnie, w zale¿noci od struktury, wytwarza-ny materia³ wêglowy mo¿na podzieliæ na zasadnicze grupy[8]:Diament obejmuj¹cy warstwy diamentowe i warstwy poli-krystalicznego diamentu sk³adaj¹ce siê z atomów o hybry-dyzacji elektronów typu ssp3.Diament nanokrystaliczny, tetraedryczny lub amorficz-ny - to nazwy u¿ywane dla podkrelenia tego, ¿e chocia¿prawie 100% atomów wêgla posiada hybrydyzacjê elektro-nów typu ssp3, to jednoczenie rozmiary krystalitów diamen-

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Rodzaje implantów: (Types of implants) • ortopedyczne

(orthopaedic) • ustne

(maxillofacial) • czaszkowo-twarzowe • (skull-facial) • dentystyczne • (dental)

Wszczepy trwa³e: (Solid (durable) implants) • protezy stawów • (artificial limbs of joints

(acetabula) • sztuczne zastawki serca • (artificial heart valves) • stymulatory serca

(heart pacemakers) Wszczepy czasowe: (Temporary implants) • p³ytki do rekonstrukcji z³amañ

koci • (plates for reconstruction of

fractured bones) • wkrêty

(screws) • gwodzie

(nails) • druty

(wires) • groty

(darts)

RYS. 1. Przyk³ady zastosowania materia³ów implantacyjnych w organizmie cz³owieka [3].FIG. 1. Examples of the application of implant materials in a human organism [3].

RYS. 2. Mikrop³ytki stosowane w chirurgii czaszki[15].FIG. 2. Mikroplates used in skull surgery [15].

RYS. 3. P³ytka stosowana w chirurgii szczêkowej[15].FIG. 3. Plate used in the jaw surgery [15].

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RYS. 6. Endoproteza stawubiodrowego [18].FIG. 6. Endoprosthesis of a hipjoint [18].

RYS. 7. Endoproteza ca³kowita stawu kolanowego [18].FIG. 7. Endoprosthesis of a knee joint [18].

RYS. 4. Implantdentystyczny[16].FIG. 4. Dentalimplant [16].

RYS. 5. P³ytka ³¹cz¹ca elementy krêgos³upa [3].FIG. 5. Plate binding the vertebrae [3].

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RYS. 11. Pow³oka DLC (SEM)[3].FIG. 11. Diamond-like carbon coating (SEM) [3].

a) diamenta) diamond

b) grafitb) graphite

c) fulerenc) fulleren

d) nanorurkid) nanotubes

RYS. 8. Odmiany alotropowe wêgla [17].FIG. 8. Allotropic forms of carbon [17].

RYS. 9. Schemat przebiegu procesu implantacjijonów: 1-pod³o¿e, 2-pow³oka, 3-wi¹zka"implantuj¹ca", 4-"rozpylana" tarcza pomocnicza[9].FIG. 9. A scheme representing the course of theions implantation process; 1 - substrate; 2 -coating; 3 - "implanting" beam; "sputtering"auxiliary shield [9].

RYS. 10. Mikrostruktura tytanu, pow..260x [19]FIG. 10. Titanium microstructure (LM), mag.260x[19].

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RYS.12. Schemat testu zarysowania (scratch testu) wraz z rys¹ wykonana w próbie [3].

RYS. 13. Wyniki testu zarysowania pow³oki wykonane na próbce z tytanu pokrytej pow³ok¹ diamentopodobn¹[3].FIG. 13. Results of the scratch test for a titanium test bar with diamond-like carbon coating [3].

§ Obci¹¿enie normalne (normal loading)

§ Si³a tarcia (friction force)

§ Wspó³czynnik tarcia (coefficient of friction)

§ Emisja akustyczna (acoustic emission)

§ G³êbokoæ penetracji (penetration depth)

§ Profil toru rysy (profile of the scratch track )

Detektor (detector)

Pow³oka (layer)

Pod³o¿e metalowe (metalic substrate) Przesuw próbki (travel of the test bar)

Rysa ( the scratch)

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towych nie przekraczaj¹ nanometrów.Wêgiel diamentopodobny (DLC) bêd¹cy mieszanin¹amorficznego lub superdrobnego wêgla, w którym przy prze-wadze wi¹zañ ssp3, w³aciwych dla struktury diamentu,wystêpuj¹ wi¹zania ssp2, w³aciwe dla grafitu (RYS.8b)) iwi¹zania sp1. Czêsto spotykana nazw¹ dla DLC jest wêgieljonowy lub wêgiel amorficzny zawieraj¹cy wodór.Karbiny: a-karbin, który zawiera wi¹zanie acetylenowe(-C=C-) i dlatego mo¿e byæ okrelany mianem poliacetyle-nu; ß-karbin, który zawiera wi¹zanie kumulenowe (=C=C=) i dlatego mo¿e byæ okrelany mianem polikumulenu.Fulereny (RYS.8c)oraz nanorurki wêglowe(RYS.8d), wktórych typowym wi¹zaniem jest tutaj, podobnie jak w gra-ficie ssp2; wytworzone warstwy zawieraj¹ zwykle miesza-ninê grafitu, fulerenów i nanorurek.Sk³ad diamentopodobnych pow³ok wêglowych zwanych wskrócie DLC (diamond like coating) nie jest jednolity, maj¹one strukturê amorficzn¹ z obszarami mikrokrystalicznymi.Ich w³aciwoci równie¿ nie s¹ okrelone w sposób jedno-znaczny, ale mog¹ siê znacznie ró¿niæ w zale¿noci odmetody u¿ytej do ich otrzymywania, poniewa¿ w zale¿no-ci od sposobu wytworzenia pow³oki zawiera ona atomywêgla o rozmaitych kombinacjach wi¹zañ.Pow³oki DLC s¹ mieszanin¹ amorficznego lub superdrob-nokrystalicznego wêgla o hybrydyzacji orbitali elektronowychtypu ssp3, ssp2, sp1, a stosunek atomów sp3 i sp2 w war-stwach uzyskanych za pomoc¹ tej samej metody silnie za-le¿y od przyjêtych parametrów nanoszenia. Tak wiêc w³a-snoci pow³oki DLC zale¿¹ nie tylko od metody wytworze-nia, ale równie¿ od parametrów nanoszenia stosowanychw danej metodzie. W³aciwoci te mog¹ zmieniaæ siê wszerokich granicach [9].Celem tej pracy by³o wiêc zmodyfikowanie powierzchni ty-tanu, zmierzaj¹ce do zwiêkszenia jego biotolerancji w or-ganimie ludzkim, poprzez wytworzenie pow³oki diamento-podobnej, a nastêpnie dokonanie oceny jej w³asnoci me-chanicznych oraz adhezji do pod³o¿a metalowego.

Materia³ i metodyka

Do wytworzenia pow³ok diamentopodobnych przeznaczo-no trzy próbki wykonane z tytanu. Próbki po odpowiednimodt³uszczeniu powierzchni acetonem a nastêpnie oczysz-czeniu jej w p³uczce ultradwiêkowej, zosta³y poddane im-plantacji jonowej celem pokrycia powierzchni metalowejpow³ok¹ diamentopodobn¹ DLC.Implantacja jonów, jest procesem wprowadzania do cia³asta³ego obcych dla tego cia³a zjonizowanych atomów do-wolnego rodzaju, dziêki du¿ej energii (od kilku do kilkusetkeV), jakiej nabywaj¹ one w pró¿ni, w przyspieszaj¹cym iformuj¹cym jony w wi¹zkê polu elektrycznym. (RYS.9.)[10]Do wybicia z powierzchni p³askiej p³yty grafitowej atomówwêgla u¿yto wi¹zkê jonów Ar+ o energii 25 keV. Wi¹zka ta("rozpylaj¹ca") bombardowa³a powierzchniê grafitu podk¹tem 67.5o wzglêdem normalnej do tej powierzchni. For-muj¹c¹ siê pow³okê bombardowano wi¹zk¹ jonów C+ oenergii 25 keV. Wi¹zka jonów C+ bombardowa³a powierzch-niê formowanej warstwy prostopadle do niej (k¹t 0o).Przed rozpoczêciem procesu formowania wi¹zkê zognisko-wano tak, ¿e jej obrazw p³aszczynie pokrywanego przedmiotu by³ prostok¹temo wysokoci 100 mm i szerokoci 5 mm. Z tego powodu wtrakcie procesu formowania pow³oki pokrywane próbki prze-suwano kilkakrotnie w poprzek wi¹zki bombarduj¹cych jo-nów C+ w celu ujednorodnienia formowanej pow³oki.Przed rozpoczêciem procesu formowania w komorze im-plantacyjnej zapewniono pró¿niê rzêdu 10-6 mbara. W trak-cie procesu formowania pow³ok mierzono pr¹dy obu wi¹-

100% of carbon atoms possess hybrid forms of electronsof the ssp type 3, the size of the diamond crystallites iswithin the range of nanometres.Diamond-like carbon (DLC) - being a mixture of amor-phous or superfine carbon in which, with prevalence of thessp3 bonds characteristic of the diamond structure, somessp2 bonds, characteristic of the graphite (FIG.8b ), and sp1bonds are present as well. The terms which are often usedfor DLC are ionic carbon or amorphous carbon containinghydrogen.Carbines: a-carbine, which contains triple carbon bonds(-C=C-) and due to this can be called polyacetylene,ß-carbine, which contains cumulene bonds (=C=C=C) andfor this reason is also known under the name ofpolycumulene.Fullerens (FIG.8c) and carbon nanotubes (FIG.8d), inwhich the typical bond is similarly as in graphite, ssp2; theformed layers usually consist of a mixture of graphite,fullerens and nanotubes.The composition of diamond-like carbon coatings, called inshort DCL, is not uniform. They have amorphous structurewith microcrystalline areas. Their properties have not beenas yet defined in a clear manner, either; they can differ con-siderably depending on the method used to produce thembecause, depending on the method of making a coating, itcan contain the atoms of carbon in various bond combina-tions.DLC coatings are a mixture of amorphous or superfine crys-talline carbon with hybridation of electronic orbitals of thessp3, ssp2 and sp1 type, where the sp3 to sp2 atoms ratio inlayers produced by the same method depends to a largeextent on the adopted parameters of application. Thus, theproperties of a DLC coating depend not only on the methodof its fabrication, but also on the spreading parameters de-termined by the method of its application. These propertiescan vary to a large extent [9].The aim of the investigations was modification of the tita-nium surface to increase its biotolerance in the human or-ganism due to the production of a diamond-like carbon coat-ing and making next an evaluation of its mechanical prop-erties and adhesion to the metal substrate.

Material and methodology

To produce diamond-like carbon coatings, three test barsof titanium were designed. The test bars after a suitabledegreasing of their surfaces with acetone and the subse-quent cleaning in an ultrasonic washer were subjected toionic implantation to cover the metal surface with a diamond-like carbon coating (DLC).Implantation of ions is the process of introducing to a solidbody ionised atoms of any type, foreign to this body, utilis-ing the great energy (from several to a few hundreds ofkeV) that they acquire in vacuum, in the electric field accel-erating these ions and forming them into a beam. [10].The diamond-like carbon coating was formed by a double-beam IBAD method. A beam of ions Ar+ with the energy of25 keV was used to "knock out" carbon atoms from the sur-face of a flat graphite plate. This "sputtering" beam wasbombing the graphite surface at an angle of 67.5° with re-spect to a normal to this surface. Thus formed coating wasbombed with a beam of ions C+ of the 25 keV energy. Thebeam of ions C+ was bombing the surface of the layer beingformed in direction perpendicular to this surface (angle 0° ).Before the beginning of the coating formation process, thebeam was focused in a way such that its image in the planeof the coated object was forming a rectangle 100 mm highand 5 mm wide. For this reason, during the process of the

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coating formation, the coated test bars were shifted severaltimes crosswise the beam of the bombing C+ ions to makethe deposited coating homogeneous.Before the beginning of the coating-deposition process, inthe implantation chamber, the vacuum of 10-6 mbar wasproduced. During the coating deposition process the cur-rents of both beams used in the IBAD process were meas-ured.As a result of the ion implantation, to the near-surface areaof the implanted material some atoms were introduced, form-ing a near-surface implanted layer of the thickness of0.01÷1µm, characterised by the physico-chemical proper-ties different than those of the core material. The course ofthe ion implantation process is schematically representedin FIG. 9.Metallographic examinations

The observations of titanium metallographic structurewere carried out under a NEOPHOT 32 optical microscope,using Weck's reagent for etching of metallographic speci-mens. As a result of observations in polarised light, the tita-nium microstructure was revealed. It is shown in FIG.10.Observation of the DLC coating was made under the scan-ning microscope STEREOSCAN 420, the result of which isshown in FIG. 11.Examinations of microhardness, of the modulus of elas-ticity gradient and of the DLC coatings adhesion totitanium surface

Testing of the mechanical properties of coatings appliedto the surface of titanium test bars and of the adhesion ofDLC coatings to the test bar surface was carried out on aMicro-Combi-Tester, made by CSEM in Switzerland. Thetester is equipped with a system for data collection and stor-ing (FIG. 13). The device satisfies the requirements of ASTMstandards regarding microhardness testers and enables:· determination of the microhardness of metallic materialsand coatings by Vickers method;· determination of the modulus of elasticity gradient of thesoft, hard, brittle or plastic materials,· conducting the scratch test in which the following param-eters are examined: normal loading, friction force, coeffi-cient of friction, the level of acoustic emission signal moni-toring the initiation of cracks in coating, the depth of indenterpenetration, and profile of the scratch track.The scratch test consisted in scratching the surface of thetested material with Rockwell stylus under a specific load(FIG.12). The values of the loading force and the stylus tippenetration depth were recorded in a continuous mannerduring the whole cycle of loading.After the test, a scratch appeared on the surface of the testbar; it was examined next under an optical microscope in-stalled on the device. The measured geometrical param-eters of the scratch, the microscopic analysis of the scratch,and the signals of acoustic emission which appeared in thecase of cracks forming in the brittle top layers of the barwere used as a source of information about the wear be-haviour and strength of the tested material.The scratch test is an effective method to determine thecoefficient of the coating layers adhesion to the substrate,a measure of which is the determined critical load Lc. Fromthe loading curve plotted in function of displacement, prop-erties such as: hardness, Young's modulus, penetrationdepth, and fracture toughness are determined. Applying aminimum stylus loading force, it is possible to take meas-urements to the depth of less than 1µm, which is of specialimportance for testing of thin coatings in the case of whichany possible effect of substrate deformation on the meas-ured properties should be eliminated.

zek stosowanych w procesie IBAD.W wyniku implantacji jonów, do przypowierzchniowego ob-szaru materia³u implantowanego zosta³a wprowadzonapewna liczba atomów, tworz¹c przypowierzchniow¹ war-stwê implantowan¹ o gruboci 0,01÷1µm o innych w³aci-wociach fizykochemicznych ni¿ materia³ wyjciowy.Badania metalograficzne

Obserwacje struktury metalograficznej tytanu przepro-wadzono przy pomocy mikroskopu optycznego Neophot 32,stosuj¹c do trawienia zg³adu odczynnik Wecka. W wynikuobserwacji w wietle spolaryzowanym, otrzymano struk-turê tytanu, pokazan¹ na RYS. 10.Obserwacje pow³oki DLC dokonano na mikroskopie ska-ningowym Stereoscan 420, w wyniku czego uwidocznionona RYS. 11.Badania mikrotwardoci, modu³u sprê¿ystoci oraz ad-hezji do powierzchni tytanu

Badania w³asnoci mechanicznych pow³ok naniesionychna próbki z tytanu oraz adhezji pow³ok DLC do powierzchnipróbek, przeprowadzono przy u¿yciu urz¹dzenia Mikro-Combi-Tester (MCT), wykonanego przez szwajcarsk¹ fir-mê CSEM, wyposa¿onego w system zbierania i archiwiza-cji wyników pomiarowych. Urz¹dzenie to spe³nia wymaga-nia norm ASTM dotycz¹cych mikrotwardociomierzy i umo¿-liwia:· okrelenie mikrotwardoci metod¹ Vickersa materia³ówmetalowych oraz pow³ok· wyznaczenie modu³u sprê¿ystoci materia³ów miêkkich,twardych, kruchych oraz plastycznych· wykonanie testu zarysowania zwanego scratch-testem, wktórym mo¿na wyznaczyæ obci¹¿enie normalne, si³ê tarcia,wspó³czynnik tarcia, wielkoæ sygna³u emisji akustycznej,zwi¹zanego z pocz¹tkiem pêkania pow³oki, g³êbokoæ pe-netracji wg³êbnika oraz profil toru rysy Test zarysowania (scratch-test) polega³ na zarysowaniupowierzchni badanego materia³u wg³êbnikiem Rockwella,który obci¹¿ony by³ okrelonym obci¹¿eniem (RYS.12).Wartoci si³y obci¹¿aj¹cej i g³êbokoci penetracji ostrzawg³êbnika by³y rejestrowane w sposób ci¹g³y w czasie ca-³ego cyklu obci¹¿ania i odci¹¿ania.Po wykonaniu testu na powierzchni próbki powsta³a rysa,któr¹ obserwowano pod mikroskopem optycznym, zainsta-lowanym na urz¹dzeniu. Mierzone parametry geometrycz-ne zarysowania, analiza mikroskopowa rysy, a tak¿e sy-gna³y emisji akustycznej, pojawiaj¹ce siê w przypadku pê-kania kruchych warstw wierzchnich próbki by³y ród³em in-formacji o charakterze zu¿ycia i wytrzyma³oci badanegomateria³u.Scratch-test jest skuteczn¹ metod¹ okrelenia stopnia przy-wierania pow³ok (warstw) do pod³o¿a, której miar¹ jest wy-znaczana si³a krytyczna LC. Na podstawie wykrelonej krzy-wej obci¹¿enia w funkcji przemieszczenia wyznaczane s¹takie w³aciwoci jak: twardoæ, modu³ Younga, g³êbokoæpenetracji, odpornoæ na kruche pêkanie. Stosuj¹c mini-malne si³y obci¹¿aj¹ce wg³êbnik, mo¿liwe jest wykonaniepomiaru na g³êbokociach poni¿ej 1µm, co jest szczegól-nie istotne podczas badania cienkich pow³ok, w przypadkuktórych nale¿y wyeliminowaæ wp³yw odkszta³cenia pod³o¿ana wyznaczane w³aciwoci.

Micro-Combi-Tester jest urz¹dzeniem umo¿liwiaj¹cymwykonywanie pomiarów twardoci klasycznymi i nowocze-snymi metodami, poprzez:- dynamiczne wg³êbnikowanie - mikrotwardoæ i modu³Younga s¹ automatycznie obliczane z krzywej g³êbokocipenetracji w funkcji obci¹¿enia przy zastosowaniu ustalo-nego modelu obliczeniowego. Twardoæ jest obliczana jakostosunek maksymalnego obci¹¿enia wg³êbnika do po-wierzchni kontaktu wg³êbnika z próbk¹ po odci¹¿eniu.

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Measurement of microhardness and of the modulus ofelasticity gradientThe Micro-Combi-Tester is a device which enables takinghardness measurements by means of the traditional andmodern methods through:· dynamic penetration - microhardness and Young's modu-lus gradient are automatically computed from the curve ofthe penetration depth in function of loading, applying theestablished model of computations. Hardness is computedas a ratio between maximum stylus loading and area ofstylus contact with the test bar surface after the load hasbeen released;· Vickers microhardness - is automatically computed by MCTsoftware, but it can also be determined directly by measur-ing the diagonals of the indentantion under the microscopeof the apparatus and further computations done by theperson taking the measurement.The measurements of microhardness were taken applyingthe following parameters [11]:· maximum stylus loading equal to 50nM;· the rate of load application and release equal to 50 mM/min,· the duration of maximum load application 5 s.

Results

Scratch testThe scratch test was conducted in three sequences:

· sequence one - the Rockwell stylus of a 200 µm radius,loaded with a force of 0.03 N, was "scanning" the test barsurface to determine its profile;· sequence two - a working movement of the stylus which,loaded with the force increasing linearly up to a value of 10N, was scratching the test bar surface along a distance of 2mm, moving at a constant velocity of 2 mm/min;· sequence three - the final stage of the test, which con-sisted in the second movement of the stylus, loaded with aforce of 0.03 N, along the scratch track to register its profileafter the load had been released (Rd).Examples of the diagrams where the results of the tests areplotted as changes of normal force, friction force, coeffi-cient of friction, penetration depth and surface profile arepresented in FIG.13.The value of the critical load Lc was determined by the tech-nique of acoustic emission from the crack which appearedin coating and optically as a result of visual inspection of

- mikrotwardoæ Vickersa - jest automatycznie obliczanaprzez software MCT, ale mo¿e byæ równie¿ wyznaczonaporednio poprzez pomiar przek¹tnych odcisku pod mikro-skopem urz¹dzenia i przeprowadzeniu dalszych obliczeñw³asnych.Pomiary mikrotwardoci wykonano stosuj¹c nastêpuj¹ceparametry[11]:- maksymalne obci¹¿enie wg³êbnika równe 50mN,- prêdkoæ obci¹¿ania i odci¹¿ania równa 50 mN/min- czas dzia³ania maksymalnego obci¹¿enia 5s

Wyniki

Test zarysowania (scratch test)Test zarysowania odbywa³ siê w trzech etapach:

- w pierwszej kolejnoci wg³êbnik Rockwella o promieniu200 µm, obci¹¿ony si³¹ 0,03N "skanowa³" powierzchniêpróbki w celu okrelenia jej profilu;- nastêpnie wykonywany by³ ruch roboczy - wg³êbnik obci¹-¿any wzrastaj¹c¹ liniowo si³¹ a¿ do wartoci 10N, na dro-dze o d³ugoci 2 mm, zarysowywa³ powierzchniê próbki,która przesuwa³a siê ze sta³¹ prêdkoci¹ równ¹ 2 mm/min;- koñcowy etap polega³ na powtórnym przejciu wg³êbnikaobci¹¿onego si³¹ 0,03N po torze rysy, w celu zarejestro-wania jej profilu po odci¹¿eniu (Rd).Przyk³adowy wykres z badañ w postaci zmian wartoci si³ynormalnej, si³y tarcia, wspó³czynnika tarcia, g³êbokoci pe-netracji oraz profilu powierzchni przedstawiono na RYS. 13.Wartoæ obci¹¿enia krytycznego Lc okrelono na podsta-wie pomiaru emisji akustycznej pojawiaj¹cej siê podczaspêkania pow³oki oraz optycznie, w wyniku obserwacji miejsc,w których nast¹pi³o jej zniszczenie (TABELA 1). Wyniki sta-nowi¹ce rednie arytmetyczne z badañ mikrotwardoci HV,modu³u Younga E oraz zag³êbienia wg³êbnika Hm w prób-ce z tytanu bez pow³oki oraz w próbce pokrytej pow³ok¹DLC znajduj¹ siê w TABELI 2.

Dyskusja

Na podstawie przeprowadzonych badañ stwierdzonowyrany wzrost twardoci (HV) próbek z warstw¹ DLC wstosunku do materia³u pod³o¿a oraz nieznacznie wiêksz¹

Metoda Method

Pomiar

Measurement

optyczna

optical

Lc

z emisji akustycznej

from acoustic emission

Lc

Wartoæ

rednia

Mean value of critical

load

N 1 6,21 5,66 5,94 2 4,34 4,92 4,63 3 5,52 5,07 5,30

5,29

TABELA 1. Obci¹¿enie krytyczne Lc wyznaczonemetod¹ optyczn¹ oraz z sygna³u emisjiakustycznej dla trzech pomiarów, wykonanych napróbce z tytanu.TABLE 1. Critical load Lc determined by opticalmethod and from the signal of acoustic emissionfor three measurements taken on titanium testbars.

Mikro-twardoæ

Micro-hardness

HV

Modu³ Younga

Young's modulus

E [GPa]

G³êbokoæ profilu

Penetration profile depth

Hm [nm]

tytan 413 ±61 136 ±14 577 ±53

DLC /tytan 747 ±67 153 ±16 461 ±50

TABELA 2. rednie wartoci wynikówpochodz¹cych z piêciu pomiarów:mikrotwardoci HV, modu³u Younga E orazzag³êbienia wg³êbnika Hm w próbce z tytanu bezpow³oki oraz w próbkach pokrytych pow³ok¹ DLC.TABLE 2. Mean values from the results obtainedon five measurements of microhardness HV,Young's modulus E and stylus tip penetrationdepth Hm in titanium test bars with and withoutDLC coating.

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the places where the coating failed (TABLE 1). The results,calculated as an arithmetic mean from the measurementsof microhardness HV, Young's modulus gradient E, andpenetration depth Hm on a titanium test bar with and with-out the DLC coating, are given in TABLE 2.

Discussion of results

Basing on the results of the carried out tests, a consider-able increase in the hardness [HV] of the test bars with aDLC layer compared to the substrate material was stated,while the value of the Young's modulus gradient was onlyslightly higher. The hardness of the DLC layer measuredwith the stylus tip penetration depth of 500 nm amounts to750 HV (about 7.36 GPa) and is lower when compared withthe data given in literature (10-25GPa) [11, 12, 13]. Prob-ably, both hardness and the Young's modulus gradient insubsurface layers are much higher, but very rough surface(resulting from the substrate roughness) makes the meas-urements with minimum stylus tip penetration impossible.Moreover, with the penetration depth of 500 nm and thelayer thickness below 1 mm, the measured values ofmicrohardness HV and Young's modulus E are affected bythe soft substrate forming local plastic areas. Low values ofhardness and Young's modulus in the tested DLC layer mayalso be due to the formation of soft areas with structuretypical of polymers.The process of the layer destruction in the scratch test isaccompanied by the emission an elastic acoustic wave, thesource of which are microcracks and material deformation.So, by analysing the signal of acoustic emission, one canalso determine the force which causes the destruction ofthe layer. In the performed tests of scratches made on theDLC layer deposited on titanium substrate, the signal ofacoustic emission (AE) was recorded after exceeding theloading of 5 N, omitting earlier, accidental, single peaks ofthe signal of this emission (FIG.12).The value of the critical load Lc = 5.3 N was determinedfrom analysis of the signal of acoustic emission and basingon visual inspection of the spots where failures occurred. Inthe places in which the layer suffered destruction, one canobserve characteristic worn-out marks, appearing first onthe edges of the groove, and next in its central part untilcomplete breaking (wearing down) of the coating runningto the substrate. Good adhesion of the layer to the substratehas generally been stated and, compared with the resultspublished in literature, the determined value of the criticalload Lc is quite satisfactory [14].The test bar has good elasticity, and in spite of the consid-erable deformation during loading, a distinct elastic springback of the test bar after release of loading can be observed.In the initial range of the loading values, i.e. up to Fn = 0.15N, the spring back after load release is complete; with theforce Fn reaching approx. 5 N, the stylus tip penetration depth(Pd) amounts to about 8 µm, and the depth remaining (Rd)after load release is 4 µm. The coefficient of friction remainsat a low level of about 0.1 till the moment when the layerbreaks completely and the stylus tip touches the substrate;then it reaches the value of 0.2, i.e. the maximum within thetested range.To enable a more comprehensive interpretation of the re-sults of the tests of micromechanical properties, a very valu-able supplement would be an analysis of the layer struc-ture, and specially the determination of the character andproportion of carbon bonds.

wartoæ modu³u Younga (E). Twardoæ warstwy DLC zmie-rzona przy g³êbokoci penetracji wg³êbnika ok. 500nm wy-nosi 750 HV (ok. 7,36 GPa) i jest mniejsza w porównaniu zdanymi literaturowymi (10-25 GPa) [11,12,13]. Prawdopo-dobnie twardoæ warstwy, jak równie¿ modu³ Younga w przy-powierzchniowych warstwach s¹ znacznie wiêksze, leczdu¿a chropowatoæ powierzchni (wynikaj¹ca z chropowa-toci powierzchni pod³o¿a) uniemo¿liwia pomiary przy mi-nimalnym zag³êbieniu wg³êbnika. Ponadto przy g³êbokocipenetracji 500nm i gruboci warstwy mniejszej od 1 mm,wp³yw na mierzone wartoci mikrotwardoci HV i modu³uYounga E warstwy, ma lokalne uplastycznienie miêkkiegopod³o¿a. Niewielka twardoæ oraz modu³ Younga badanejwarstwy DLC mo¿e byæ spowodowana równie¿ tworzeniemsiê miêkkich obszarów o strukturze charakterystycznej dlapolimerów.Procesowi niszczenia warstwy w tecie zarysowania towa-rzyszy emisja sprê¿ystej fali akustycznej, której ród³em s¹mikropêkniêcia oraz deformacja materia³u. Zatem na pod-stawie analizy sygna³u emisji akustycznej mo¿na okreliæsi³ê, która w tym samym czasie powoduje zniszczenie war-stwy. W wykonanych testach zarysowania warstwy DLC napod³o¿u tytanu, sygna³ emisji akustycznej (AE) zarejestro-wano po przekroczeniu obci¹¿enia 5N, pomijaj¹c wczeniej-sze przypadkowe, pojedyncze piki AE (RYS.12). Wartoæobci¹¿enia krytycznego Lc=5,3N okrelono na podstawieanalizy sygna³u AE oraz obserwacji miejsc, w których wy-st¹pi³o jej zniszczenie. W miejscach wystêpowania znisz-czenia warstwy, zauwa¿yæ mo¿na charakterystyczne wy-tarcia, pocz¹tkowo na brzegach bruzdy, nastêpnie w jejrodkowej strefie, a¿ do przerwania (przetarcia) pow³oki dopod³o¿a. Generalnie stwierdzono dobr¹ adhezjê warstwydo pod³o¿a, a w porównaniu z wynikami literaturowymi,wyznaczona wartoæ obci¹¿enia krytycznego Lc stanowizadawalaj¹c¹ wartoæ [14].Próbka posiada dobr¹ sprê¿ystoæ, a pomimo du¿ego od-kszta³cenia przy obci¹¿eniu, obserwuje siê znaczny powrótsprê¿ysty próbki po odci¹¿eniu. W pocz¹tkowym zakresie(do obci¹¿enia Fn=0,15N) po odci¹¿eniu jest to powrót ca³-kowity, przy sile Fn ok. 5N g³êbokoæ penetracji ostrza (Pd)wynosi ok. 8 µm, a g³êbokoæ pozostaj¹ca (Rd) po odci¹-¿eniu odpowiednio 4 µm. Wspó³czynnik tarcia utrzymuje siêna niskim poziomie ok. 0,1 do momentu przerwania war-stwy i styku ostrza wg³êbnika z pod³o¿em, osi¹gaj¹c mak-symaln¹ wartoæ 0,2 w badanym zakresie.W celu szerszej interpretacji wyników badañ w³aciwocimikromechanicznych cennym uzupe³nieniem by³oby wyko-nanie analizy struktury warstwy, zw³aszcza okrelenie cha-rakteru i proporcji wi¹zañ wêglowych.

Wnioski

Z dotychczasowych wstêpnych badañ tytanu przepro-wadzonych w ramach niniejszej pracy wynika, ¿e metodawytwarzania pow³ok diamentopodobnych technik¹ implan-tacji jonowej daje zadowalaj¹ce wyniki w³asnoci mecha-nicznych i adhezji do pod³o¿a, pod warunkiem bardzo sta-rannego przygotowania powierzchni pod³o¿a .Przeprowadzone badania pozwoli³y na sformu³owanie ogól-nych wniosków:1. Modyfikacja warstwy wierzchniej próbek wykonanych ztytanu, ochronnymi pow³okami diamentopodobnymi (DLC),przyczyni³a siê do utworzenia na próbkach, nowej jakociszczelnych warstw wierzchnich, maj¹cych na celu zwiêk-szenie biotolerancji materia³u, w porównaniu z tradycyjny-mi implantami metalowymi.2. Uzyskane pow³oki diamentopodobne wykaza³y dobr¹adhezjê do pod³o¿a metalowego oraz korzystne zmiany

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Conclusions

From the initial studies of titanium, which have been car-ried out so far within the framework of this work, it followsthat the method of manufacturing diamond-like carbon coat-ings by means of ions implantation gives satisfactory re-sults as regards the mechanical properties and adhesion tothe substrate, providing that the substrate surface has beenvery carefully prepared.The investigations carried out so far allowed formulatingthe following conclusions:1. The modification of a top layer on test bars made oftitanium and protected with diamond-like carbon coatings(DLC) contributed to the formation on these test bars of thetight top layers of a new quality, increasing the materialbiotolerance in comparison with the traditional metal im-plants.2. The obtained diamond-like carbon coatings showed goodadhesion to the metal substrate and advantageous changesof micromechanical properties of the surface, i.e. an essen-tial improvement of substrate microhardness and increasedwear resistance of the tested bars.3. The microscopic observations revealed a satisfactoryhomogeneity of structure on the coating surface and accrossits thickness.4. In the future, when making coatings by the method ofionic implantation, attention should be paid to the necessityof very careful preparation (washing and cleaning) of themetal surface before implantation.5. The technology of the ionic implantation, which offers thepossibility of implanting any element at low temperature,allows maintaining unchanged the shape and dimensionsof the treated objects.

Acknowledgements

The microstructural examinations were performed at theFoundry Research Institute in Cracow, the diamond-likecarbon coatings DLC were applied onto titanium test barsat the Institute of Nuclear Physics in Cracow, the adhesionof DLC coatings to titanium substrate was tested at theDepartment of Machine Design and Terotechnology, Fac-ulty of Mechanical Engineering and Robotics, AGH Univer-sity of Science and Technology in Cracow. The support andassistance of all these organisations is hereby gratefullyacknowledged.

w³asnoci mikromechanicznych powierzchni, a mianowicie:nast¹pi³ istotny wzrost mikrotwardoci pow³oki w stosunkudo mikrotwardoci pod³o¿a oraz wzrost odpornoci na zu-¿ycie badanych próbek.3. Obserwacje mikroskopowe wykaza³y zadowalaj¹c¹ jednorod-noæ strukturaln¹ na powierzchni oraz na gruboci pow³oki.4. W przysz³oci, wykonuj¹c pow³oki metod¹ implantacjijonowej nale¿y zwróciæ uwagê na koniecznoæ bardzo pre-cyzyjnego przygotowania (mycia i czyszczenia) powierzch-ni metalu przed implantacj¹.5. Technologia implantacji jonów, maj¹ca mo¿liwoæ implan-towania dowolnym pierwiastkiem w niskiej temperaturze,pozwoli³a na zachowanie niezmiennoci kszta³tu i wymia-rów elementów obrabianych.

Podziêkowania

Badania mikrostrukturalne tytanu zosta³y wykonane wInstytucie Odlewnictwa w Krakowie, pow³oka diamentopo-dobna DLC na próbkach z tytanu zosta³a wytworzona wInstytucie Fizyki J¹drowej w Krakowie, a badania adhezjipow³oki DLC do powierzchni tytanu wykonano na Akade-mii Górniczo-Hutniczej w Krakowie, w Zak³adzie Konstruk-cji i Eksploatacji Maszyn.

Pismiennictwo References[1] John Enderle i in.. Introduction to Biomedical Engineering. El-sevier Biomaterials Science, Rok 2005[2] Buddy D.Ratner i in.. Elsevier Biomaterials Science. An intro-duction to Materials in Medicine. Rok 2003.[3] Biel Go³aska M., ¯uczek R., Warmuzek M.: Dobór materia³uoraz warstwy powierzchniowej na implanty metalowe. Praca na-ukowo-badawcza Instytutu Odlewnictwa zl-2066/00. Kraków 2003.[4] Shi, Biomaterials and Tissue Engineering. Rok 2004, Wydaw-nictwo Springer.[5] Ku H.: Problemy biocybernetyki i inzynierii biomedycznej. TomIV Biomateria³y. Wyd. Komunikacji i £¹cznoci, Warszawa 1990.[6]. Marciniak J.: Biomateria³y.. Wydawnictwo Politechniki l¹skiej,Gliwice 2002.[7] Bêdziñski R.: Biomechanika in¿ynierska. Zagadnienia wybra-ne. Oficyna Wydawnicza Politechniki Wroc³awskiej. Wroc³aw 1997.[8] Mitura S., B¹kowski K., Bogus³awski G. i in.: Nanokrystalicznydiament dla medycyny.. In¿ynieria Materia³owa 2000, Tom. 21, Nr3, str. 120-124.[9] Qi Jun and al.: Mechanical and tribological properties of non-hydrogeneted DLC film synthesized by IBAD. Surface and CoatingsTechnology 128-129 (2000), str. 324-328.[10] Burakowski T. Implantacja jonów do metalu, Prace InstytutuLotnictwa, Nr 2-3, Tom 121-122, Warszawa 1990, str.5-51[11] Rakowski W., Kot M., Zimowski S., Badania adhezji i mikro-twardoci pow³oki DLC na próbkach metalowych, Raport Labora-torium Tribologii i In¿ynierii Powierzchni, Kraków, styczeñ 2005[12] Grabarczyk J. Louda P., Niedzielski P., Poprawa adhezji warstwdiamentopodobnych do pod³ozy z WC-Co przy wykorzystaniu me-tody RF PACVD, Inzynieria Materia³owa, Nr 5/2005, str. 274-276[13] Platon F., Fournier P., Rouxel S.: Tribological behaviour ofDLC coating compared to different materails used in hip joint pro-stheses., Elsevier, wear 250(2001) str. 227-236[14] Yoshinori F., Kaoru A., Haruyuki Y., Tadaaki S.: Adhesionstrength of DLC films on glass with mixing layer prepared by IBAD.Surface and Coatings Technology 128-129 (2000), str. 308-312.[15] http://www.chm.pl[16] Implantoprotetyka, Tom I, Nr.1, Wrzesieñ 2000[17] http://www.fulleren.com.pl[18] http://www.chifa.com.pl[19] Biel Go³aska M., Warmuzek M., ¯uczek R., Improvement ofthe titanium surface with a diamond-like carbon coatings, Europe-an Congress on Advanced Materials and Processes, 5-8 wrzesieñ2005, Praga.naptycznego.

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PULSED CATHODIC ARC PLASMATECHNOLOGY DEPOSITION OFTHROMBORESISTANTNANOSTRUCTURAL CARBONCOATING ON COMPONENTS OFARTIFICIAL HEART VALVES

E.I. TOCHITSKY

PLASMOTEG SCIENCES ENGINEERING CENTRE OF FTI OF NATIONAL

ACADEMY OF SCIENCES OF BELARUS

1/3 KUPREVICH ST., MINSK, 220141, BELARUS.E-MAIL: [email protected]

Abstract

This paper describes the results of applying ofpulsed cathodic-arc plasma (PCAP) method forma-tion in vacuum biocompatible and thromboresistant t-a carbon coatings on the components of artificial heartvalves (AHV).The special pulsed arc plasma source was used forevaporation of the graphite cathode to form pulsedaccelerated carbon plasma flows and deposited themon polished samples of titanium alloys and compo-nents AHV made of the same alloys. Influence of theinitial voltage of cathode arc discharge in range of100÷450V and temperature of substrate during thedeposition in the range 293÷773oK on structure, phasecomposition, hardness and biomedical properties coat-ings were investigated .The results of investigation of biomedical propertiest-a carbon films deposited by PCAP method haveshown that the best biocompatibility andthromboresistivity have the nanostructural carboncoatings with cluster size 10-20nm and thickness0,08÷0,1 microns. The artificial heart valves with de-posited nanostructural t-a carbon coatings were im-planted on ten animals (dogs). The obtained resultshave shown that the passing of blood through AHVleads to moderate activation of coagulation processes.


Introduction

Nowadays biological and mechanical artificial heartvalves (AHV) are successfully used to treat heart valve func-tion disorders. Comparison of there two kinds of AHV hasdiscovered, that biological prosthesis causes lessthrombogenity but it has shorter mechanical durability andlife period. It wears out rather quickly, valve insufficiency isdeveloped, the valve doesn¢t close property. MechanicalAHV has longer mechanical durability and is resistant towear [1]. Its life period is more that 30 years. However itinjures blood elements shapes, causes blood coagulationprocess activation, that results in developing ofthromboembolitic complications.

The problem of creating biomaterials for artificial humanorgans, especially artificial heart valves, arises from anumber of specific requirements connected to their influ-ence on living body. A material should not be toxic, allergic,traumatizing living tissue, it should be resistant to wear andmechanical destruction and should not cause hemoles andblood coagulation, change its structure and surface con-figuration, transform chemically or decompose [2, 3]. Such

metals and alloys as stainless steel, Ti, Ta, Co-Cr and oth-ers have received the greatest spreading as biomaterialsfor medical purposes. But side by side with such merits ofthese materials as high strength, long life, good technologyof treatment, they have great shortcomings, such as bio-logical incompatibility, not sufficient resistance to the influ-ence of biological environment, and excite allergy. This prob-lem can be solved by protection of an implant surface withspecial coatings [4, 5].

Methods of preparation and examinationDLC coatings

The special pulsed are plasma source was used forevaporation of the graphite cathode to form acceleratedpulses carbon plasma flows and to deposit them on pol-ished titanium alloys samples and AHV components. Thedeposition conditions were as follows: initial voltage of arcdischarge 100÷350V, arc current amplitude 2000÷3500A,pulse energy 10÷150J, pulse frequency 5÷8Hz, pressure ofthe vacuum chamber~10-3Pa, substrate temperature293÷673oK.

Transmission electron microscope (TEM) JEM 200CXwas used to investigate structure of the DLC films.

Raman and X-ray photoelectron spectroscopies wereemployed to characterize the chemical atomic bond andcomposition of the DLC coating. The photoelectronspectrometer EC-2401 with Mg-Ka radiation (hw=1253.6 eV)was used.

Nanohardness was measured by Scanning Probe Mi-croscope and nanotribology was determined by Digital Scan-3100 (both made of Digital Instruments).

Medical tests were carried out with blood of ten dogswhich had implanted AHV with DLC coating.

Results and discussion

Contact of an alien material with blood leads to forma-tion of a blood plasma albumen layer on the material sur-face, the dynamic of composition and structure alteration ofwhich to a great extend determines physicochemical andbiocompatible properties of an implant surface. As it is shownby results of scientific research and practical surgery withorgans implantation the best biocompatible and medico-bio-logical properties have the surfaces with minimal value ofinterface free energy of implant's surface and biologicalhabitat which are composed of interchanging hydrophile andhydrophobe domains with size less than 10-50nm (i.e.nanostructural surfaces). If such conditions are observedthe surface absorbs a minimal albumen quantity easily in-terchangeable with blood plasma albumen what results inthe rise of bio- and hemocompatibility of the implant. TheDLC coatings are the more preferable [6-11]. Carbon coat-ings don't have general toxic, allergenic and carcinogenicinfluence and they aren't histotoxic. These coatings arethromboresistive, biocompatible with blood sells don't makeinfluence on blood plasma albumen and don't change ac-tivity of plasma enzymes.

We produces biocompatible thromboresistant DLC coat-ings manufactured from pulsed flows of carbon plasma bythe method of pulsed cathodic-arc deposition. The resultsof DLC coatings deposition in vacuum on the AHV compo-nents from titanium alloy VT16 are presented. The influ-ence of the initial voltage of cathode arc discharge in therange of 100-450V and the temperature of AHV compo-nents during the deposition in the ranges of 293 -773oK onstructure, phase composition, adhesion, tribology and hard-ness of DLC coatings were investigated. The deposited

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after its partial evaporation. This gives the constant diagramof distribution of accelerated plasma flows. In the plasmasource the discharge ignition is executed by a dischargebetween the ignition electrodes 4 and 5, having the contactwith thin film conductor 2 deposited on a dielectric 6. Thesolenoid 7 is used to increase the discharge stability igni-tion. The plasma source anode unit is composed by an an-ode 8 and a focusing solenoid 9. The assembly of genera-tor units is effected by the clamps 10. A control semicon-ductor valve 11 is used for discharges commutation. Theignition capacitor 12 of 10-20µF is discharged by this valve.The pulse arc discharge is made by energy of capacitorsbattery 14 having a capacity of 2-4 thousand of microfarads.

The generator works in the next consecution. After ob-taining in the vacuum chamber on which is fixed the gen-erator the pressure less than 10-3 Pa, the capacitor bank12 is charged up to a voltage of 500 - 800V, and the capaci-tors batteries 13 and 14 is charged up to 150-400V. Thecontrol signal going on the valve 11 perform the dischargeof the capacitor bank 12. The appearing current pulse evapo-rates the film conductor 2 and creates the appearance ofinitiating plasma in the area of the localised electrical con-tact on the electrode 5 and cathode 1. The plasmoid cre-ates a conductivity channel between the cathode 1 and theignition electrode 5. This is excite the discharge of the ca-pacitor13 and forming of the cathode spots. The material ofevaporated in the cathode spot is almost fully ionised. Theplasma jets expend in all directions and some fraction ofthe plasma makes contact with anode.

The further development of the initiating discharge bringto filling of the space between the cathode 1 and the anode8 by the plasma what due to the beginning of a main dis-charge by the energy accumulated in the capacitors battery14. The solenoid 9 create a magnetic field to focus andaccelerate plasma. It is generate plasma flows of cathodematerial. The necessary coating is formed from depositedplasma flows on the surface of manufacturing articles.

The FIG.2 presents the oscillograms of alteration of dis-charge current between the plasma source electrodes inthe process of one pulse. The curve 1 shows the dischargecurrent alteration between the ignition electrodes (unit scale100 A), the curve 2 shows the main discharge current al-teration between the cathode and the anode (unit scale1000A). The time of the ignition pulse is 25 µs, the time of

particles in our process are usually high energetic ions (car-bon is once ionized at 98%). High ionization takes placedue to a very high power density presenting at the surfaceof the feedstock material, i.e. carbon in the case of dia-mond-like carbon. Deposition by high energetic ions hastwo advantages. The first advantage is that the ions reactmore likely with the substrate than with neutral atoms andmolecules and the second advantage is that usually at im-pact of high energy ions, which embed partially into substratesurface. As a result dense, inorganic coatings with an ex-cellent adhesion can be deposited virtually on any material.All our pulsed plasma processes were executed in a vacuumchamber with a base pressure of about 10-3Pa. The pulsedplasma discharge was formed by a short-time electrical arcerosion of cathode material by extremely hot microspots ofa vacuum arc discharge. In addition the plasma can be ac-celerated with a Hall-type plasma accelerator and directedtowards the substrate where a coating is deposited.

The generation of the pulsed plasmoids is obtained byshort-term electrical erosion of cathodic material by hot ca-thodic microspots of pulsed vacuum arc, burning on the in-tegral "cool" surface. The plasma flows or plasmoids, peri-odically generated by the Hall's arc accelerator, were ac-celerated and directed onto the substrate, fixed in thesubstrate holder. As a result of condensation of the plasmoidmaterial thin films and coatings are formed on the substratesurfaces.

A new Hall's pulsed accelerator of electroerosive plasmafor technological purpose has been designed and devel-oped to realise the pulsed method [12]. The plasma sourcegives a possibility to obtain the thin films and coatings onthe base of metals, their allows and combinations of nitrides,carbides etc, and also of diamond-like carbon.

The scheme of without contact ignition plasma source ispresented in the FIG.1. The plasma source has ignition sys-tem which to use a localised electrical contact between cath-ode 1 and the thin film conductor 2, deposited on the sur-face of an insulator 6. In our plasma source the above lo-calised contact moves from pulse to pulse by the cathode1. A such technical design provide a high discharge ignitionprobability and practically avoid the erosion of an insulator,providing a long life of the ignition system.

The plasma source consists from three main units: acathode unit, an anode unit and a discharge ignition unit.The cathode unit has the main plasmaforming expendableelectrode - the cylindrical cathode 1 which is fixed on theend of cooling cathode holder 3. There is a bellows whichallow to move the cathode in the plasma generation zone

FIG. 1. Schematic illustration of the Hall'splasma accelerator used for pulsed arcdeposition DLC coatings.

FIG. 2. Oscillogram of the parameters disharge

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the main erosion pulse is 200 µs. The integral current be-tween the cathode and the anode is determined by the curve3.

The current of plasma going through Longmur probesensor (the curve 4) is measured during the discharge. Thecontribution of ion current in the plasma flow is approxi-mately 10% of the arc current. Electrons of plasma reachthe probe in 8 µs after main pulse beginning and ions ofplasma reach the probe only after 240µs. The electricalcurrent is provided by a flow of electrons from the cathodeto the anode which is significantly faster than the velocity ofthe ions. The electron velocity was 1.5×107cm/sec and theion velocity was 0.5×106 cm/sec, difference 30 times.

Our experiments have shown that the deposited DLCfilms have a good adhesion with different materials ofsubstrate. The DLC films exhibited a density mass up to 3.4g/cm3, electrical specific resistance at different conditionsis from 104 up to 109 Ohm×cm, the temperature of struc-tural transformation to graphite was higher than 673oK [13].TABLE 1 shows the results of comparison of some proper-ties of DLC films with natural diamond and carbon films pre-pared by using other methods.

For explain the film properties we have conducted com-plex studies of their structure, chemical and phase compo-sition by electron microscopy, Raman and photoelectronspectroscopies, nanohardness and nanotribology [13].

DLC films deposited on surface AHV components havethickness 0.5÷0.2µm. therefore for measurement of hard-ness it's necessary to use nanohardness. The result ofmeasurements were shown that DLC films hardness de-pends from condition of deposition and achieves hardnessof natural diamond up to 100GPa.

Chemical composition investigation performed by meansof X-ray photoelectron spectroscopy method has shown that

the deposited DLC films have the same chemical composi-tion as the graphite cathode. The DLC films have carbon98% and oxygen 2%, but the graphite cathode has a littlemore oxygen.

The films have a low content of impurities. The totalamount of impurities is ~3% on layers surface of a thick-ness of 5nm, and in deeper layers it is less than 2%. Themain impurity was oxygen and while secondary impurity ionmass spectroscopy analysis showed the presence of tracesof Cr,Fe,Ni, which probably concerns the sputtering ofvacuum chamber parts.

The results of electron microscopy and diffraction analy-sis indicate that the quasiamorphous disordered phase con-

tains crystalline inclusions of different carbon modifications,with size 5÷15 nm (FIG. 3). At the same time one can seelarger crystalline inclusions with diamond structure. Crys-talline inclusions have a comparatively small volume in films,therefore the quasiamorphous phase has the main influ-ence on DLC-films properties.

The electron diffraction patterns of the quasiamorphousphase in carbon films exhibits from two to six diffusive ringswhich may differ by their position, intensity and shape invarious samples and can be described by that of small clus-ter models. It was found that DLC films deposited frompulsed vacuum plasma flows represent a nanostructuralcondensate with ordered nanoclasters of a size of about0.5-2.5 nm with coherently dispersed electrons (FIG. 4) andhave a diamond structure which organize clusters more lar-der sizes 5÷15 nm. Between these nanoregions there arecarbon atoms located in disorder.

Different DLC films properties are due to different corre-lation of sp, sp2 and sp3 atomic bonds [14-16]. It was shownthat possible changing the deposition conditions to obtain

TABLE 1. Properties of diamond and DLC films.

FIG. 3. TEM image and a diffraction pattern ofnanostructure of the DLC film.

FIG. 4. The dependence of Csp3 atomic bonds andLc area size of coherent electron scattering onmain discharge voltage Ud for substratetemperature of 293oK and 573oK.

Properties Diamond films CVD

Hydrogenized films α-C:H

Arc plasma deposition films tα-C

Diamond (Type II)

Microhardness (GPa) 70-90 18-40 40-100 57-100 Young's modulus (GPa) 986-1050 50-150 450-600 1079 Density (g/cm3) 3.5 1.8-2.4 2.4-3.4 3.52 Friction coefficient, up to 0.05 - 0.05 0.05 Resistivity (Ohm⋅cm) up to 1012 10-1014 104-109 1014 Thermal conductivity (W/m⋅°K) 600-1800 0.2-0.5 3-9 2000 Refraction index (λ=583nm) 2.4-2.45 1.7-2.3 2.4-2.7 2.44

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DLC films with the predominance of tetrahedral (sp3-dia-mond) types of bonds between carbon atoms. Determina-tion of bonds between carbon atoms C-C sp3 and C-C sp2

is realized using X-ray photoelectron and Ramanspectroscopy. For example FIG. 4 shows the correlation ofthe number of sp3 bonds on main discharge voltages fordifferent substrate temperatures. One can see that this de-pendence has a non-linear behavior. Diamond type sp3

bonds are most prevalent with main discharge voltage of300V. It was ascertained that the properties of both DLC-films prepared by pulsed vacuum arc plasma deposition andall DLC film-titanium substrate samples have high chemi-cally inert and biocompatible.

On the base of investigations of DLC coatings propertydependence on deposition conditions there were chosenoptimal parameters of cathodic-arc evaporation of graphitetarget with formation of carbon plasma flows and their con-densation on surface of substrates from titanium alloys VT-16 and on components of AHV made of VT-16 alloy. Theinvestigation results have shown that the deposition of DLCcoatings increase considerably wear resistance and chemi-cal fastness of researching alloys. DLC coatings of 0.08-0.1µm thickness were deposited on AHV components atdifferent deposition modes and than was executed a medico-biological testing of AHV to determine their thrombogenityand biocompatible.

Comparative experiments with dogs were executed todiscover the effectiveness of DLC-coating details AHV [17].The AHV "PLANEX" was implanted to 14 dogs (1 group)and AHV "PLANEX" with DLC coatings was implanted to10 dogs (2 group). For both groups autocoagulography co-agulation period was defined in 8 and 10 minutes to deter-mine the first hemostasia phase. The protrombin index, fi-brinogen A level, the prothtrombin period of spontaneousand euglobulin fibripoliosis were defined to determine thesecond hemostasia phase.

The data of venous and aortic coagulography periphericblood as well upper and bellow the AHV implantation wereanalyzed to expose the AHV influence on hemostasia sys-tem. TABLE 2 demonstrates the results of the investiga-tions.

A month later after the implantation a well-noticeable

hypercoagulation and increased level of fibrinogen A wereobserved in the peripheric blood of the dogs (group 1). Co-agulation indexes approached the normal in the dogs (group2) which were implanted AHV with DLC coatings. The co-agulation period was increased, PTI index came back toinitial state, the number of fibrinogen A and hematocritisfigures were decreased. Thus brightly expressedthrombogenios influence of AHV "PLANEX" without DLCcoatings on the blood coagulation system on both local andsystematic levels was preserved for a month.

Conclusion

According to results of thrombogenity investigations therewere optimized the conditions of DLC- coatings depositionon AHV components and there were prepared AHV whichwere implanted to animals. For determine the thrombogenityof AHV the blood for analysis was taken before and afterimplanted AHV. Coagulogramme was studied during onemonth. The obtained results have shown that the passingof blood through AHV leads to moderate activation of co-agulation processes. The AHV with DLC coatings whichprepared by pulsed cathodic arc plasma deposition havevastly less thrombogenity than the AHV without DLC coat-ings.

AHV with DLC coatings influenced much less expres-sively hypercoagulating on the central and peripherical bloodstream starting with the first month in the body. Taking intoconsideration, all the above mentioned should be recom-mended preferably to apply in clinical practice.

References

[1] Y.P. Ostrovsky., Disk artificial hart valves Planex, J. Engen.Phys. and Thermophys., 69, 3, 478-488 (1996) (in Russion).[2] Gotman, Characteristic of metals used in implant., J. Endouro-logy Dec.11(6), 383-389 (1997).[3] E.Knott, H. Reul, M. Knoch et.al., In vitro comparison of aorticheart valve prostheses, Part 1: Mechanical valves, J. Thorac. Car-diovasc. Surg., 96, 6, 952-961 (1998).[4] H.S. Tran, M.M. Puc, C.W. Hewitt et al., Diamond-like carboncoatings and plasma or glow discharge treatment of mechanicalheart valves, J. Invest. Surg., 12, 133-140 (1999).[5] E.I. Tochitsky, O.G. Sviridovich, N.M. Beliavsky, Deposition ofBiocompatible Thromboresistant Coatings from Pulsed Plasma onArtificial Heart Valves, VI Int. Conf. Plasma Physics and PlasmaTechnol.- Proceedings Book, 2, 471-474, Minsk, Belarus, Septem-ber 15-19, 2003.

Control group

After an AHV implantation

1-3 days 1 month

Indices n=10 1 group

(n=14) 2 group (n=10)

P

1 group (n=9)

2 group (n=7)

P1 <

P2<

Time of coagulation in non siliconized test-tube (sec)

491.0±12.l 347.2±13.8 660.0±ll.6 0.001 366.0±23.2 432.0±6.7 0.05 0.001

Time of coagulation in siliconized test-tube (sec)

688.5±12.5 412.2±80.8 780.0±8.9 0.05 532.0±66.2 794.0±18.5 0.05 0.5

Autocoagulogramme 8 min 13.8±0.3 15.2±0.9 13.0±0.6 0.5 12.0±0 20.6+0.6 0.001 0.001 10 min 16.7±0.3 15.6±1.2 14.0±l.2 0.05 12.3±0.8 24.6±0.8 0.001 0.001 PTI % 86.3±3.2 94.4±3.7 96.5+14.1 0.5 89.3±4.9 78.2±4.6 0.001 0.06 Fibrinogen A (mg) 96.6±4.7 296.0±35.9 126.6±l.0 0.05 371.6±35.6 123.0±4.7 0.05 0.001 Tolerance of plasma to heparine (sec) 231.0±3.2 112.0±10.8 188.0±22.0 0.1 100.0±56.3 147.4±6.2 0.008 0.06 Thrombus time (sec) 28.3±1.9 27.4±0.9 29.0±l.2 0.5 21.8±1.4 25.0±1.7 0.05 0.005 Fibronolisis euglobuline (sec) 3324±33 3442±48 3090±17 0.001 3412±41 2620±101 0.001 0.003 Hematocryte 45.0±0.9 47.8±5.2 41.0±0.6 0.05 48.3±4.2 40.4±l.0 0.05 0.5 where: P – truth of data comparison after 1-3 days and data of control group P1 - truth of data comparison after 1 month and data of control group P2- truth of data comparison after 1 month and 1-3 days after operation

TABLE 2. Coagulation data of the peripheral bloodof dogs after implantation AHV with the DLCcoating.

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[6] Dion, C. Baquery, J.R. Monties, Diamond: the biomaterial ofthe 21st century, Inter. J. Art. Org., 16, 623-627 (1993).[7] Dion, X.Roques, C. Baquey, et. al., Hemocompatibility of dia-mond-like carbon coating, Biomed. Mater. Eng., 3, 51-55 (1993).[8] L.Lu., M.W. Jones, Diamond-like carbon as biological compati-ble material for cell culture and medical application, Biomed. Ma-ter. Eng., 3, 223-228 (1993).[9] L Tang, C.Tsai, W.W. Gerberich et. al., Biocompatibility of Che-mical Vapour Deposited Diamon, Biomaterials, 16, 483-488 (1995).[10] L.A. Thomson, F.C. Law, N. Rushton, Biocompatibility of dia-mond-like carbon coating, Biomaterials, 12, 37-40 (1991).[11] M.I. Jones, I.R. McCol, D.M. Grant et.al., Hemocompatibility ofDLC and TiC-TiN interlayers on titanium , Diamond and Related,8, 457-462 (1999).[12] E.I. Tochitsky, O.V. Selifanov, V.V. Akylich et.al., ElectricalErosion Pulsed Plasma Accelerators for preparing Diamond-likeCarbon Coatings, Surf. and Coat. Techn., 47, 522-527( 1991)[13] E.I. Tochitsky, A.V. Stanishevskii, I.A. Kapustin, et.al., Structu-re and properties of carbon films prepared by pulsed vacuum arcdeposition, Surf.and Coat. Techn., 47, 292-298 (1991).[14] A.V. Stanishevsky, E.I. Tochitsky, Formation of MetastableCarbon Film Structure by pulsed Arc Plasma deposition in Vacu-um, J of Chemical Vapor Depos., 4, 297-310 (1996).[15] T.L. Parker, K.L. Parker, I.R. McColl et.al., The biocompatibili-ty of low temperature diamond-like carbon films: transmissionelectron microscopy, scanning electron microscopy and cytotoxi-city study, Diamond and Related Mater., 3, 1120-1123 (1994).[16] Y.X. Leng, J.Y. Chen, P. Yang et.al., Mechanical propertiesand platelet adhesion behavior of diamond-like carbon films syn-thesized by pulsed vacuum arc plasma deposition, Surface Scien-ce, 531, 177-184 (2003).[17] S.I. Korsak, Thrombogenous artificial vales Planex of depen-dence from type of surface coating, Zdravookhranenie, 8, 14-18(1997) (in Russion).

THE CHLORINATED SYNTHETICDIAMOND SURFACEINTERACTION WITHC-NUCLEOPHILES

V.V. KOROLKOV, B.N. TARASEVICH,I.I. KULAKOVA, G.V. LISICHKIN

DEPARTMENT OF CHEMISTRY,LOMONOSOV MOSCOW STATE UNIVERSITY,LENINSKIE GORY 1, BUILD.3, MOSCOW, 119992, RUSSIA


Abstract

Several reactions of C-nucleophiles with the chlo-rinated surface of two types of diamond were imple-mented. Detonating nanodiamond "UDA-SF" and syn-thetic diamond "DALAN" have been employed in theabove procedures. The incorporation of butyl and ni-trile groups has been achieved. However the incor-porating of phenyl groups via reaction with PhLi is stilla problem. For the first time NMR-H1 spectroscopy ofsuspension was used for elucidating structure of graft-ing compound was proposed.

Keywords: nanodiamonds; grafting compounds;surface chemistry; chemical functionalization.


Introduction

There is an escalating interest in diamond chemistry to

nanoscale diamonds in recent years [1]. It is due to severalreasons. The first is that nanodiamonds (ND) became com-mercially available only in last ten years [2]. The secondand obviously the most significant ones are their uniqueproperties which combine mechanical, termic, radio andchemical stability of diamond as well as lability of functionalcover of surface. The latter is determined by large value ofspecific surface area in ND. In various patterns of NDs spe-cific surface area is about 300 m2/g or less whereas in thecase of natural or synthetic diamonds powders the value ofspecific surface area usually is about several metres pergram. Such large value of specific surface area of NDs sub-stantially increases possibilities of their further chemicalmodification and moreover enlarges the field of potentialapplication of diamond materials. Among the most attrac-tive utilizations of NDs are biomedical applications(nanoparticles for drug carry in vivo) and development ofnew chromatographic materials, especially for HPLC.

Also stable hydro- and organosoles of NDs are requiredfor many technological applications. Therefore the problemof chemical modification of ND particle surface is of currentimportance. Besides modification of ND surface is attrac-tive as a technique for unification of surface chemical state.

Notwithstanding the fact that NDs is a promising mate-rial the number of works concerning chemical modificationof its surface is rather modest [3,4,5]. Therefore investiga-tions on controlled chemical creation of grafting compoundson the ND's surface are of fundamental and technologicalimportance.

Experimental

In the present work two types of diamond were employed:detonation nanodiamond "UDA-SF" and synthetic diamondpowder "DALAN". "UDA-SF" is typical nanodiamond withthe size of aggre-gates no more then 0.04 µm and specificsurface area 245 m2/g (BET measurement). Synthetic dia-mond powder "Dalan" used represents itself a polydispersepowder with the size of particles from 5 nm up to 10 mi-crons with a specific surface area of 22 m2/g (BET meas-urement).

Chemical state of diamond particles was characterizedusing Fourier-transform spectroscopy (IR200Thermonicolet), NMR-H1 - spectroscopy (Bruker-Avance-400).

Results and discussions

It is necessary to mention that in native state the surfaceof diamond powder is covered by different oxygen contain-ing groups (for ex. alcohol, carboxyl, carbonyl and othersthat is firmly confirmed by infrared spectra [6,7]), i.e. thesurface is polyfunctional. And this fact complicates any fur-ther chemical reactions on the diamond surface due tononselectivity of their passing. Consequently thepolyfunctionality arises the problem of unification of diamondsurface in order to make reactions that are carried out on itto be selective.

The most common procedure of unification, and moreo-ver the only one, consists in hydrogen stream treatment ofdiamond at 1073 or 1173 K for 4 or 5 hours. These condi-tions are sufficient to modify the diamond surface in a wayof hydride group's layer formation (Scheme, FIG.1).

It should be noted that specific surface area of diamondpowder is slightly affected by this treatment as determinedby BET analysis. So, after such treatment we obtained afully hydrogenated diamond surface that is confirmed byIR-spectra presented (FIG.2).

As we can see from spectra, after such treatment stretch-

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ing vibration related to C=O-group disappeared whereastwo stretching vibrations of CH - bonds appeared. In thecase of "UDA-SF" (FIG.3 spectra c and d) very strong ad-sorption of hydroxyl groups (3400-3500 cm-1) is present evenafter hydrogen treatment.

By the way with the loss of polyfunctionality of the dia-mond surface we also have lost its reac-tion capacity withinthe formation of the CH-bonds on the surface.

In order to activate the surface in terms of electrophile centercreation it was subjected to chlorination. Chlorination was per-formed in two ways. In case of "DALAN" chlorination was car-ried out by treating sample with sulfurylchloride in the pres-ence of azobisisobutyronitrile (AIBN) in benzene in Ar ambi-ent at 50-60oC. Photochemical chlorination by molecular chlo-rine dissolved in carbon tetrachloride was employed in case of"UDA-SF". As it was found by elemental analysis this treat-ment resulted in the ultimate chlorinated diamond surface for-mation. It is worth to point out that further treatment of "DALAN"with sulfurylchloride is yielded in sulfonylchloride group's layer

formation.Speaking of chlorinated diamond powder one should al-

ways keeps in mind that "fully chlorin-ated" doesn't meanthat all surface bonded hydrogen atoms are substituted bychlorine. It only means that no further chlorination is possi-ble under described conditions and that is due to steric hin-drance or repulsion between chlorine atoms on the surface.

Further reactions of chlorinated of both types of diamondswere carried out after an exhaustive vacuum evaporationof the reaction mixture. The chlorinated diamond powderwas then treated with n-BuLi (2.5M solution in hexane). The

butylation was carried out by stirring the suspension at 25oCfor 24 h under an argon atmosphere. It should be noted thatinitially reaction mixture was subjected to ultrasonic treat-ment (50 Wh, 35±10% KHz) for 1.5 hours. The reactionwas then terminated by adding water to the solution. Thepowder was then repeatedly washed with acetone, etherand water to remove LiCl and other organic by-products,and was dried in vacuum (<1 mm Hg.) for several hoursand then characterized by FTIR spectroscopy.

This makes it possible to incorporate n-butyl groups ontothe diamond surface which clearly seen from IR-spectrapresented (FIG.3).

As it can be obviously seen from spectra presented thenew vibrations appeared in the region of 3000-2800 and1500-1300 reciprocal centimeters that are related to stretch-ing and bending vibra-tions in alkyl chains, i.e. in butyl groupsbonded to the diamond surface. Also frequencies assignedto stretching and bending vibrations of alcohol groups ap-peared too.

IR spectroscopy supplies us only with qualitative data.We can only see appearance or disap-pearance of certainbands in spectrum but very little can be gathered about thestructure of grafted sub-stance. In order to precisely deter-mine the structure of surface groups we have proposed asimple tech-nique utilizing NMR-H1 spectroscopy. We havecollected NMR-H1 spectrum of suspension of n-Bu-UDA-SF in CDCl3 (FIG.4). And it clearly indicates the presenceof n-Bu group on the diamond sur-face.

Reaction of phenyl lithium (1.2M solution in Et2O) withchlorinated diamond surface of "DALAN" was carried out inthe same manner as with butyl lithium. FTIR spectra pre-sented bellow (FIG.5).

But unfortunately the interpretation of IR-spectra ofphenylated diamond surface isn't so vivid as with butylateddiamond surface. For instance none of CH-bond stretchingvibrations can be observed in spectra whereas bending vi-brations (1488 and 1431 cm-1, 1504 and 1434 cm-1 ) arepre-sent. Thus in this case direct evidence of Ph-group graft-ing on to the diamond from IR-spectra cannot be obtained. Inorder to prove phenyl groups bonding to the diamond sur-face we treated phenylated diamond "Dalan" with nitratingmixture (hydrogenated diamond was also treated in the sameway for comparison). In the case of phenylated diamond a

HHH

HH

H

HH

H

H

H

HH

HHHH HHH

HH

HH

HH

HH

HHH

HOHO H

O

O

OH

OH

O OO

OH

O

O

H OHO

O

OO O

HOOH

OHHO

O

H O

OHO

O H

H2-treatment

FIG. 1. Scheme. Reduction of diamond surface.

FIG. 2. FTIR spectra: a, c - pristine "DALAN" and"UDA-SF", b, d - the same diamonds afterhydrogen stream treatment at 800oC for 5 h.

2953

2925

2861

1629

1561

1459

1374

1320

969 72

662

1

2955

2927

2852

1657

1601

1463

1371

1220

1173

.05

.1

.15

.2

Abs

orba

nce

3500 3000 2500 2000 1500 1000 500 Wavenumber (cm-1)

Butylated UDA-SF

Butylated Dalan

FIG. 3. FTIR spectra of butyklated samples ofDALAN and UDA-SI.

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new adsorption at 1536 and 1347 cm-1 has appeared andthese are due to antysimmetrical and symmetrical vibrationsin NO2 - group in -C6H4-NO2 - fragments formed during nitra-tion (FIG.6). No adsorption at 1536 and 1347 cm-1 was foundin the case of hydrogenated diamond.

Thus we get an indirect evidence of incorporation of phe-nyl groups onto the diamond surface.

Our attempts to incorporate phenyl groups onto the "UDA-SF" surface via reaction with PhLi obviously have failed.On FIG.7 one can see FTIR spectra for the pristine, hydro-gen treated and subjected to phenylation "UDA-SF".Phenylation was performed by adding a solution of PhLi inEt2O (obtained via exchange reaction: n-BuLi + PhBr) tophotochemically chlorinated for 24 hours "UDA-SF". FTIRspectra of treated sample clearly indicates that no phenylgroups are incorporated onto the surface at appreciableconcentration. The only result of such treatment is only ad-ditional hydroxylation of diamond surface.

Nitrile group on the diamond surface is very attractivedue to various possible ways of its trans-formation. So as toincorporate cyanide groups on to the surface of "DALAN"and "UDA-SF" a solution of sodium cyanide in anhydrousdimethylsulfoxide was added to chlorinated diamond pow-der. The reaction was carried out by stirring the suspension

at room temperature for 24 h. The powder was then filtered,repeatedly washed with water and acetone, dried and char-acterized by FTIR spectroscopy (FIG.8). In both cases FTIRspectra showed strong disappearance of the CH-bondstretching vibrations but only in "UDA-SF's" spectrum newfrequency ascribed to CN-group vibrations have appearedat 2223 cm-1. The most evident reason explaining this factis low concentration of nitrile groups on the surface of"DALAN" which has comparatively small specific surfacearea (22 m2/g).

ConclusionReactions of several C-nucleophiles with chlorinated dia-

mond surface were investigated and new modified diamondswith n-butyl and nitrile groups were obtained. For the firsttime NMR-H1 spectroscopy of suspension was proposedto elucidate structure of grafting compounds that can behelpful for fast and precise determination of organic func-tional groups on the surface.

FIG. 4. Utilization of NMR-H1 spectroscopy ofmodified diamond suspension for elucidationstructure of grafting compounds (by ex. ofbutylated UDA-SF).

3724

3675

1625

1488

1431

1217

1157

1082

1001

865

479

3413 29

2228

49

1634

1501

1434

1223

1155 10

8210

3486

4

503

.9

.95

1

1.05

1.1

1.15

1.2

Abs

orba

nce

3500 3000 2500 2000 1500 1000 500 Wavenumber (cm-1)

a

b

FIG. 5. FTIR spectra of phenylated DALAN: a -sample was treated with SO2Cl2 for 22 hours andthen treated with PhL obtained via exchangereaction n-BuLi+PhBr in Et2O; b - sample wastreated with SO2Cl2 for 8 hours and then treatedwith PhLi obtained via reaction of met. Li withPhBr in Et2O.

FIG. 6. FTIR spectra of phenylated DALAN andthe same sample subjected to nitration by mixtureof HNO3 and H2SO4.

3687

2940

2878

1637

1330

1136

837

2934

2877 16

3115

54

1333

1147

3683 29

29

1740

1629

1559

1387

1125

829.2

.4

.6

.8

1

1.2

1.4

Abs

orba

nce

4000 3500 3000 2500 2000 1500 1000 500 Wavenumber (cm-1)

a

b

c

FIG. 7. FTIR spectra: a-pristine UDA-SF, b-hydrogen treated, c-phenylated.

2936

2883

2223

1628

1534

1316

1120

1620

1448 10

87.02

.04

.06

.08

.1

.12

.14

.16

Abs

orba

nce

4000 3500 3000 2500 2000 1500 1000 500 Wavenumber (cm-1)

a

b

FIG. 8. FTIR spectra: a-NC-DALAN, b-NC-UDA-SF.

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References

[1] Dolmatov V. Yu. Detonation synthesis ultradispersed diamonds:properties and applications // Russ. Chem. Rev. - 2001. - 70, 7. - P.607-626.[2] V.V. Danilenko On the History of the Discovery of Nanodia-mond Synthesis // Physics of the Solid State - 2004. - 46, 4. - P.595-599.[3] Y. Liu, Z. Gu, J. L. Margrave, V. N. Khabashesku Functionaliza-tion of Nanoscale Diamond Pow-der: Fluoro-, Alkyl-, Amino-, andAmino Acid-Nanodiamond Derivatives // Chem. Mater. - 2004. -16, 20. - P. 3924-3930.[4] Yu Liu, V. N. Khabashesku, N. J. Halas Fluorinated Nanodia-mond as a Wet Chemistry Precursor for Diamond Coatings Cova-lently Bonded to Glass Surface // JACS. - 2005. 127, 11. - P. 3712-3713.[5] A. Xiaoning, Z. Hanmin Functionalization of carbon nanobeadsand their use as metal ion adsorb-ents // Carbon - 2003. - 41, 15. -P. 2889-2896.[6] Jiang Tianlai, Xu Kang, Ji Shengfu FTIR studies on the spectralchanges of the surface functional groups of ultradispersed diamondpowder synthesized by explosive detonation after treatment in hy-drogen, nitrogen, methane and air at different temperatures // J.Chem. Soc., Faraday Trans. - 1996. - 92, 18. - P. 3401-3406.[7] T. Jiang, K. Xu FTIR study of ultradispersed diamond powdersynthesized by explosive detonation // Carbon. - 1995. - 33. - P.1663-1671.

GROWTH OF CELLS ON CARBONCOATINGS MANUFACTURED INNEW MW/RF REACTOR

I. UBRTOVÁ*, L. GRAUSOVÁ**, L. BAÈÁKOVÁ**,W. KACZOROWSKI***

*DEPARTMENT OF MATERIAL SCIENCE, TECHNICAL UNIVERSITY OF

LIBEREC, CZECH REPUBLIC

**INSTITUTE OF PHYSIOLOGY, ACADEMY OF SCIENCES OF THE

CZECH REPUBLIC, PRAGUE, CZECH REPUBLIC

***INSTITUT OF MATERIAL SCIENCE, TECHNICAL UNIVERSITY OF

LODZ, POLAND


Abstract

Due to unique physico-chemical properties andgood biocompatibility are carbon layers consideredto be promising material for wide field of biomedicalapplications. In this study, carbon films weremanufaktured in microwave and radio frequencyplasma reactor using dual frequency method (MW/RF PCVD - microwave and radio frequency plasmachemical deposition). Four various processes of depo-sition were used for preparation layers on substratesof medical stainless steel AISI 316 L. On samples ofall four processes, growth and adhesion of cells wereobserved.[Engineering of Biomaterials, 56-57,(2006),19-21]

Experimental details

Materials and deposition procedureIn the present study we have studied carbon coatings

(NCD) prepared in microwave and radio frequency plasmareactor using dual frequency method MW/RF PCVD - mi-

crowave and radio frequency plasma chemical vapour depo-sition. Parameters of the deposition were optimised to getuniform films on the stainless steel AISI 316L. Stainlesssteel substrates used in the present study were shaped as2,5 mm thick circular discs with diameter of 8 mm. Substrateswere machined, electropolished, ultrasonically cleaned inmethanol and dried. Prior to NCD deposition, the surfacewere cleaned in an argon inert plasma in the vacuum cham-ber for 10 minutes. [1] Four various processes of deposi-tion were used TAB. 1. In present paper, coated sampleswere named after number of deposition process, uncoatedwere just AISI 316L.Cells and cultures conditions

Coated and uncoated samples were sterilized in steamautoclave by temperature 120°C for 20 minutes, immersedin tissue water. All samples were placed into polystyrenemultidishes (Costar, 24 wells, diameter 15 mm) and seededwith human osteosarcoma cell line MG 63 and Dulbeccomedium at the initial density 30 000 cells/well. Glasscoverslips and the polystyrene dish as control materials wereused. Cells were cultured for one, three and seven days inthe temperature of 37°C in atmosphere containing 5% ofCO2. On day one and three after seeding, the cells wererinsed in phosphate-buffered saline (PBS), fixed with 70%cold ethanol (-20°C, 5 min), vizualized by propidium iodide(5µg/ml, 5min). Their morphology was evaluated and docu-mented using epifluorescence microscope IX 50 equippedwith a digital camera DP 70 (Olympus, Japan). Fluorescentcell linker kit PHK 26 RED and propidium iodide for bettervizual representation, were used. The number of adheringMG 63 cells was counted in 10-16 randomly selected mi-

TABLE 1. Parameters of deposition processes.

PROCESS Methane

[%]

Bias

[V]

Power

[W]

Pressure

[Pa]

Time

[min]

1. 30 400 150 10-60 6

2. 30 500 250 10-30 3

3. 20 600 250 10-25 4

4. 15 700 250 10-30 5

FIG. 1. Number of initially adhered osteoblast-likeMG 63 cells on tissue culture polystyrene(Cult.dish), on glass coverslips (Glass), uncoatedsample AISI 316 L, Sample 1, 2 , 3, 4 on day 7 afterseeding. Average ±SEM from 10-16measurements, statistical significance incomparison with values obtained on culture dish.

Cell population density on day 7

0

200000

400000

600000

800000

1000000

1200000

Cult.dish

Glass AISI316L

Sample1

Sample2

Sample3

Sample4

Cel

l num

ber

/ cm

2 Cell number / cm 2 SEM

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croscopic fields (20x objective, 1 and 3 day after seeding).On day 7 after seeding, when the cell counting in micro-scopic field was disabled by a high cell population densityand formation of multi-layered areas, the cells were detachedby trypsin-EGTA for 5 min at 37°C and counted in a Bürkerhomeocytometer (18 measurements for each sample). [2,3]

Results

On day 1 after seeding, the number of cells initialy ad-hered on all samples was lower than found on conventionaltissue culture polystyrene dishes and than on glasscoverslips. In comparison with uncoated sample AISI 316 Lwas the number of cells on coated samples significantlyhigher. Morphology of osteoblast-like MG 63 cells on day 1after seeding is represented in FIG.3. From day 1 to 3 afterseeding, the cell number on all samples incresased in thefollowing order: Polystyren > Glass > Sample 1 >AISI 316 L> Sample 4 > Sample 3 > Sample 2. On day 1 and 3 afterseeding, clear preference of cell growth on edges of sam-ples was observed. Clusters of cells on edge areas of sam-

ples were detected, but in the middles of samples only iso-lated cells were found. On day seven the higher prolifera-tion activity of cells on the all coated samples in compari-son to uncoated sample was observed. The most numberof adhering cell were on polystyrene culture dish and on theglass coverslips. Non of our samples has better cell adhe-sion. In comparison with coated samples has higher number

of cells the Sample 3 than Sample 2, Sample 1 and AISI316L (FIG.1). Average cell numbers were compiled asgrowth curvers (FIG. 2A). The population doubling time DTof MG 63 cells between day 3-7 was shortest for Sample 3(FIG. 2B), followed with Sample 2, Culture dish, Glass, Sam-ple 4, Sample 1 and AISI 316L. Statistic data were pre-sented as means ± S.E.M. from 10-16 measurements ob-tained from 1 sample for each experimental group. Statisti-cal significance was evaluated by the Student's t-test incomparison with values obtained on polystyren culture dish.

SEM observation were performed in VEGA TS 5130scanning electron microscope. The results of observation

FIG. 2. Number of initial adhered osteoblast-likeMG 63 cells (A) growth curves of these cells fromday 0-7 (B) the population doubling time DTbetween days 3 and 7 after seeding on tissueculture polystyrene (Cult.dish), on glasscoverslips (Glass), uncoated sample AISI 316Land coated Sample 1, 2 , 3, 4.

FIG. 3. Morphology of osteoblast-like MG 63 cellson day 1 after seeding, stained with propidiumiodide or red fluorescent cell linker,epifluorescence (A) culture dish polystyrene (B)glass coverslips (C) sample 1 (D) sample 2 (E)sample 3 (F) sample 4, (G) AISI 316 L, (H) nativecells in medium on culture dish.

1 000

10 000

100 000

1 000 000

10 000 000

-1 0 1 2 3 4 5 6 7 8Day after seeding

Log

cell

num

ber

/ cm

2

Cult. dish Glass AISI 316 L Sample 1

Sample 2 Sample 3 Sample 4

0

10

20

30

40

50

60

70

80

90

Cult. Dish Glass AISI 316L Sample 1 Sample 2 Sample 3 Sample 4

DT

(ho

d)

DT (hod) SEM

A B

A B C D

E F G H

FIG. 4. SEM micrographs of surfaces of coatedsamples; photo on left side presents edge ofsample, right is the middle of the sample (A)sample 1 (B) sample 2 (C) sample3 (D) sample 4

C

A B

D C

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were presented in the FIG.4. Different surface morphologyof layers on samples could be one of the reasons to growthpreference of cells on individual samples. It may be thecause of the growth preference of cells on the edge areasof samples with comparison to the middle areas of sam-ples, where on day 1 and 3 after seeding rather isolatedcells were found.

Conclusion

In this study growth and proliferation of osteoblast-likecells MG 63 on four carbon films deposited under differentprocess conditions in MW/RF reactor were investigated. Inthis paper the comparison of cell growth on coated,uncoated, glass and tissue culture polystyren was per-formed. We have noticed potential dependence of cell ad-hesion on surface morphology on edges and in the middleof sample. This study may be helpful in a selection of coat-ing conditions in MW/RF reactor to create suitable carbonfilms for biological application.

Acknowledgements

We thank Mgr. Lubica Grausova for maintaining the cellline MG 63 in culture and excellent technical assistance bytests. Special thanks to MUDr. Lucie Baèáková, CSc. formaking available test and for all support. We thank Ing.Witold Kazcorowski for preparing the carbon films. We wouldalso like to thank Ing. Vladimír Kovaèiè and Ing. JanaGrabmüllerová (Department of textile materials, TechnicalUniversity of Liberec) for observations on scanning elec-tron microscope.

References

[1] Kaczorowski W., Niedzielski P., Mitura S.: Manufacture of car-bon coating for biomedical applications in a new MW/RF reactor.Engineering of Biomaterials, 43-44, (2005), 28-31 ISSN 1429-7248.[2] Baèáková L., Jungová I., Slosarczyk A., Zima A., PaszkiewiczZ.: Adhesion and growth on human osteoblast like MG 63 cells incultures on calcium phosphate-based biomaterials. Engineering ofBiomaterials, 38-43,(2004), 15-18.[3] Baèáková L., Lapèíková M., Kubies D., Rypáèek F.: Adhesionand growth of rat aortic smooth muscle cells on lactide-based po-lymers. Tissue Engineering, Stem Cells and Gene Therapies. Edi-ted by Y. Murat Elçin, Kluwer Academic/Plenum Publishers, Volu-me 534, 2003, 179-189.

ELECTRIC POTENTIAL OFBIOMATERIALS COATED WITHDIELECTRIC CARBON LAYERAND NON-COATED IN WATERAND SERUM

S. URBAÑSKI*, P. NIEDZIELSKI*, S. MITURA*,T. WIERZCHOÑ**, A. SOKO£ OWSKA*

*INSTITUTE OF MATERIALS SCIENCE AND ENGINEERING,TECHNICAL UNIVERSITY OF LODZ;90-924 LODZ, STEFANOWSKIEGO 1/15 STREET, POLAND

**FACULTY OF MATERIALS SCIENCE,WARSAW UNIVERSITY OF TECHNOLOGY;02-507 WARSAW, WO£OSKA 141 STREET, POLAND


Abstract

Electric potentials, established in water and humanblood serum, of the electrodes made of platinum,graphite, Ti6Al4V alloy, TiN, AlSi316L steel, oxidizedsteel and the materials coated with diamond like car-bon layer (DLC) and a nanocrystalline-diamond layer(NCD) were determined. The values of the potentialsof non-coated materials increased with increasingelectron work function (F) of investigated materialsin reasonable accordance. The difference between thepotentials measured in serum and in water was as-cribed to the differing molecular electron structure ofthe proteins in contact with the electrodes. Electrodepotentials of different materials coated with the samethin dielectric carbon layer varied significantly depend-ing on the F value of the substrate. In this way theselection of a substrate material permits influencingon the interaction between NCD (DLC) coating andserum compounds. The potential of an electrode hasappeared to be a simple but sensitive indicator of thephenomena that take place on the biomaterial sur-face.

Keywords: electrode potential, electron work func-tion, Pt, TiN, carbon, Ti6Al4V, AlSI316L, DLC, NCD.


Introduction

The bulk biocompatibility of implant materials (i.e., thesimilarity of their mechanical, magnetic etc. properties tothe properties of the human body) can be evaluated in themacro-scale in a quite simple way by in vitro examinations.The interaction between the surface of the implant materialand the tissues, blood and cells is usually examined in vitroby observing the phenomena in the microscopic scale us-ing biological methods. The specific drawback of the bio-logical methods carried out in vitro lies in the necessity ofusing certain additional substances, absent in the living or-ganism, that ensure the stability of the specimen. Moreo-ver, the results of biological examinations obtained by vari-ous investigators are difficult to compare. Simple physico-chemical methods suitable for estimating macroscopicallythe biocompatibility of the implant surface are scarce. Theyprimarily include corrosion examinations and tracing thepresence of the markers of selected bio-chemical processesthat proceed in blood.M.J. Jones et al. [2], who examined the haemocompatibility

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Experiments

Measuring methodThe potential of the electrode in the liquid examined was

determined by measuring the voltage established betweenthe reference electrode, which was an EK602 calomelminielectrode of a potential of +223 ±5 mV, with respect tothe potential of the saturated chinhydron electrode consid-ered to be equal to zero according to the Geneva Conven-tion.

The voltage was measured using a MERAU722A elec-tronic voltemeter with the inner resistance RW=109W and asensitivity of 10mV.]

MaterialsThe liquids examined were de-ionized water and a fresh

human blood serum obtained from drug-free volunteers, atpH=7.2 and a temperature of 300K.

The examinations included biomaterials whose signifi-cance seemed prospective for the applications where theimplants were to be in contact with blood. Polymer materi-als were omitted, chiefly because their effectiveness de-pends on the 'micro-architecture' of the implant made ofthem [10]. The electrode materials used in the experimentsare given in TABLE 1.

TiN was formed on a Ti6Al4V alloy substrate by subject-ing it to glow discharge assisted d.c. nitriding in nitrogen ata temperature of 1123K, as described in [13]. Diamond-like carbon (DLC) was produced on a Ti6Al4V alloy substrateby the pyrolysis of methane in an r.f.-frequency plasma at atemperature of 573K. The nanocrystalline diamond (NCD)layer was produced on a Ti6Al4V alloy substrate using thepyrolysis of methane in an r.f.-frequency plasma at a tem-perature of 873K as described in [14]. The AlSI316L steelwas oxidized by heating at 728K in air as described [11].


FIG. 1 shows the results of measurements of the elec-trode potentials in H2O (ewater) and the values of the electronwork function (F) of the non-coated materials. The resultsclassify the materials according to growing ewater as follows:Pt>graphite>oxidized steel>TiN. The same sequence is truewhen ordering according to increasing F.

The Ti6Al4V alloy and AlSI316L steel differed from theother materials. The value of their ewater depended stronglyon the time for which the electrode was immersed in water(FIG. 2). This observation seems to suggest that the metal-lic ions have passed to the water and confirms thatelectrochemical corrosion occurs in both materials [11,12].ewater of oxidized steel remained constant, which confirmsthe results obtained by Chun-Che Shih et al. [11]. The meas-urement of ewater permitted us to reveal, quickly and immedi-

of Ti, TiC, TiN and DLC, combined a macroscopic physicalmeasurement (surface tension in respect to water) and achemical measurement (haemoglobine release into plasma)with microscopic biological examinations (platelets attach-ment). These three methods yielded similar results as tothe ordering of the biocompatibilities of the materials exam-ined. The measurement of the surface tension was the sim-plest and absolutely 'non-invasive'. Similar attempts at re-lating the surface tension with the haemocompatibility weremade by J.A. McLaughlin et al. [3], X. Wang et al [4], andB.J. Hunt et al [5]. The relation between the hardness andthe surface biocompatibility was studied by L.A. Thomsonet al. [6].

In our previous work [1] we made an attempt to relatethe electric potential of an electrode immersed in water (ewater)

with its electron work function (FM). The preliminary resultsshowed a reasonable agreement between ewater and FM,although the spread of the values was quite wide.

The present study was concerned with an attempt at uti-lizing the electric potential of an electrode made of the bio-material examined as the indicator of the interaction be-tween the components of a given biological medium andthe electrode surface. Contrary to the commonelectrochemical corrosion investigation we only consideredthe effects of the electron transfer from the electrode intomolecules of the surrounding medium. The materials whoseions passed into water were not examined, chiefly becausethey may be toxic for a living body. Therefore we did notused the equilibrium equation between a metal and its ionexpressed as

where µ - electrochemical potential, F - Faraday number, a- activitybut we solely measured the contact potential V (Volta volt-age) related to the electron work function (FM) of the bio-material and to the charge neutrality level (CNL) of the mol-ecule, given by

The contact potential between solids has been describedfor electronic purposes using the band model theory (7). Thesame theory was used for describing the solid-molecule con-tact [8]. Although the band structure of a molecule differsfrom the band structure of a solid, it has been proved that theeffects that occur at the solid-molecule contact are analo-gous to those that take place between two different solids.When examining the Au-perylene-tetra-carboxylic-dianhydride molecule contact, these authors observed abroadening of molecular bands at the contact with the metaland ascribed this to the electron hopping interaction FAu6S-

Fmol. The mechanism associated with the formation of Me-Molecule interface barrier involves the charge transfer be-tween the two materials due to a weak chemical interaction.As a result an electrostatic interface dipole is formed, whichtends to align the metal Fermi level and the molecule chargeneutrality level.

For example, J.Ristein et al [9] described the contactpotential of an H-terminated diamond surface with H2O atpH6 to be a result of the electro-chemical potentials of thetwo bodies becoming equilibrated. Since, under these con-ditions, C- H shows a negative electron affinity, diamondfunctions as an electro-donor in this contact.

lnM MM R

RTa

zF zF

µ µϕ ϕ⊕−− = +

e

Investigated biomaterial ÖM [eV] References Platinum 5,32-6,35 [15] Graphite 4,0-4,7 [15] AlSi316L Fe-4,31 [15] Ti6Al4V Ti-3,9 [15] Fe2O3 3,8 [15] TiN 3,75 [17] NCD/DLC 3,0 [16]

Investigated fluid H2O Srerum

TABLE 1.

statessurfaceelectronE FM +=Φ

MV C NL= Φ −

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rials were changed, the sequence according to growing eserum

followed the increase of F and ewater values.The potential difference eserum - ewater should be an expres-

sion of the phenomena that occur at the biomaterial-serumcomponents boundary. As shown in FIG.4, the electrodesmade of various materials differed in their eserum - ewater valueroughly in accordance with the increase of their ewater. Thedifference (eserum-ewater) of Pt was the largest. The (eserum- ewater)of graphite and TiN were smaller, but almost the same, anddid not follow the ewater sequence. Therefore, TiN appearedto be an exceptionally surface-active biomaterial.

The results may be described in terms of the existenceof the contact potential at a solid-protein junction and thespace charge built of negatively charged ions similar to the

ately, any metal dissolution, an effect very undesirable whendealing with biomaterials.

The values of non-coated electrode potentials in serum,eserum, are shown in FIG. 3. When immersed in serum, theelectrodes behaved in a similar way as in water. Althoughthe electric potentials eserum of the individual electrode mate-

FIG. 4. eserum - ewater of noncoated materials.

270 276

350 356

0

100

200

300

400

(mV)

Graphite TiN AlSi316Loxidised

Pt

504

421392

0

100

200

300

400

500

600

AlS i316L +NCD

TiN + NCD Ti6Al4V +NCD

(mV)

A

1 6 3

1 1 71 0 3

02 04 06 08 0

1 0 01 2 01 4 01 6 01 8 0

(m V )

A lS i3 1 6 L +N C D

TiN + N C D Ti6 A l4 V +N C D

b

FIG. 5. Electrode potentials of carbon NCD layercoated materials: a) ewater of NCD, b) eserum of NCD,c) ewater - eserum of NCD.

341

304289

260

280

300

320

340

360

AlSi316L +NCD

TiN + NCD Ti6Al4V +NCD

(mV)

c.

291

6,35 eV

202

4,7 eV

43

3,8 eV

53

3,75 eV

1

10

100

1000

Pt Graphite AlSi316Loxidised

TiN

FIG. 3. Electrode potentials in serum eserum ofnoncoated materials.

130

140

150

160

170

180

5 10 15 20 25 30t (m in)

(m V)

0

20

40

60

5 10 15 20 25 30t (min)

(mV)

FIG. 2. Electrode potentials in water ewater of:a)Ti6Al4V, b)AlSI316L.

FIG. 1. Electrode potentials in water ewater andelectron work function F of noncoated materials.

63 7

6,3 5 e V

47 3

4,7 eV

39 3

3,8 eV

32 9

3,7 5 e V

1

10

10 0

10 00

(m V )

P t G ra phite A lS i31 6 Loxid is ed

T iN

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References

[1] A.Soko³owska, S.Mitura, T.Wierzchoñ, P.Niedzielski, K.Orliñ-ska, P.Sawosz, In¿ynieria Biomateria³owa 7 (2004), 55.[2] M.J. Jones, I.R. Mc Coll, D.M Grant., T.L. Parker: Diamond Relat.Mater. 8 (1999) 457.[3] I.A. Mc Laughlin., B.Meenan, P.Maguire, N.Janieson: DiamondRelat. Mater. 5 (1996) 486.[4] X. Wang, F.Zhang, Ch.Liu, Zh.Zheng, X.Liu, A.Chen, Zh. Jiang,Surf a Coat, Tech. 128-129 (2000) 36[5] B.J. Hunt, R.Paratt, M.Cable, D.Finch, M.Yacomb, Blood Co-agul. Fibrinolysis 8 (1997) 223.[6] L.A.Thomson, F.C.Law, N.Rushton, J.Franks, Biomaterials 12(1991) 37.[7] E.Spenke, Elektronische Halbleiter, Springer Vrlg., Berlin, He-idelberg, N.Y. 1965.[8] H.Vazquez, F.Flores, R.Oszwaldowski, J.Ortega, R.Perez,A.Kahn, Appl. Surface Science 234 (2004) 107.[9] I.Ristein, M.Riedel, F.Maier, B.F.Mantel, M.Stammler, L.Ley,J.Phys, Surface of diamond, Condens. Matter 13 (2001) 8979.[10] L.Siemiñski, K.J.Goch, Biomaterial - interactions, Biomate-rials 21 (2001) 2233.[11] Chun-Che Shih, Chun-Ming Shih, Yea-Yang Su, Lin Hui JulieSu, Man-Song Chang, Shing Jong Lin, Corrosion Science 46 (2004)427.[12] D.F.Williams, Titanium: Epitome of biocompatibility or caux forconcern, J. Bone Joint. Surg. 76 (1994) 348.[13] E.Czarnowska, T.Wierzchoñ, A.Maranda, E.Kaczmarewicz,J.Mater. Sci.: Mat. In Med. 11 (2000) 73.[14] S.Mitura, E.Mitura, A.Mitura, Diamond a Rel. Mat. 4 (1995)302[15] W.Formienko, Emisjonnyje swojstwa materja³ow - sprawoæ-nik, Kijew, Naukowaja Dumka, 1970.[16] R.J.Nemanich, P.K.Bauman, M.C.Benjamin, O.-H.Nam,A.T.Sowers, B.L.Ward, H.Ade, R.F.Davis, Appl. Surf. Sci. 130(1998) 694.[17] G.V.Samsonov , J.M.Vinitskij: " Hamdbok of Refractive Com-pounds" J.S.J Plenum 1980.

CARBON FIBRE-BASED POSTSWITH CEMENTIT UNIVERSALRESIN CEMENTATION SYSTEMAS A MATERIAL FORRESTORATION OFENDODONTICALLYCOMPROMISED TEETH - SEMEVALUATION OF SEALING

BANASZEK KATARZYNA*, KLIMEK LESZEK**

*DEPARTMENT OF ENDODONTICS, MEDICAL UNIVERSITY OF £ÓD,UL POMORSKA 251, 92-213 £ÓD, POLAND

**INSTITUTE OF MATERIALS ENGINEERING,TECHNICAL UNIVERSITY OF £ÓD,STEFANOWSKIEGO 1/15, 90-924 £ÓD, POLAND

EMAIL: [email protected]


Introduction

Dental caries or mechanical injuries can result in sub-stantial loss of hard tissues of the tooth crown. Teeth withpartially or completely destroyed coronary structure can stillfunction in the oral cavity provided they undergo root canaltreatment and prosthodontic reconstruction with posts and

Helmholtz-Stern layer.The electrodes made of the metals coated with thin di-

electric layers (NCD, DLC) behaved in different way as thenon-coated electrodes (FIG. 5, 6). Their e depended first ofall on the kind of the substrate materials in particular on itsF and not on the F value of NCD, DLC. So it appeared,that a selection of a substrate metal permits changing theinteraction between NCD, DLC layer surface and serumcomponents.

Conclusion

The measurements of the electric potential e of various elec-trodes immersed in water and human serum show that thisparameter (e) is sensitive to the dissolution of the metal and tothe electron energy structure of the solid-molecule contact.Therefore, the value of e seems to be a quick and simple pre-liminary indicator of the biocompatibility of a material.

The measurements of e of thin dielectric carbon layers(DLC, NCD) deposited on various conducting materialsshow, that the surface biocompatibility of NCD, DLC coat-ings can be affected by electron properties of theirsubstrates.

411

357294

0

100

200

300

400

500

AlSi316L +DLC

TiN + DLC Ti6Al4V +DLC

(mV)

a.

8 5

6 7

3 9

01 02 03 04 05 06 07 08 09 0

(m V )

A lS i3 1 6 L +D L C

T iN + D L C T i6 A l4 V +D L C

b .

326290 255

050

100150200250300350

AlSi316L +DLC

TiN + DLC Ti6Al4V +DLC

(mV)

c.

FIG. 6. Electrode potentials of carbon DLC layercoated materials: a) ewater of DLC, b) eserum of DLC,c) ewater - eserum of DLC.

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3000N SEM.The evaluation of sealing was performed in the apical

part of the post by determining the width of the gap be-tween the carbon fibre post and the resin cement, as wellas the post and the root canal dentin.

For the obtained results, arithmetic mean and standarddeviations were calculated. To verify the formulated hypoth-eses the parametric test of significance based on small sam-ples was used.

Additionally, the analysis of the carbon fibre post struc-ture was performed in the light microscope basing on longi-tudinal sections and cross-sections of the posts.

Results

The general view of the restored tooth is presented inFIG.2a, while FIG.2b shows a magnified fragment of thecarbon fibre post.

The results of gap width measurements in the examinedteeth restored with carbon fibre posts are depicted in TA-BLE 1.

In the teeth studied the adhesion between the post and

the resin cement as well as between the resin cement andthe dentin was very good (FIG. 3). Only in same places, thepresence of a few-micrometer gaps was sporadically ob-served (FIG. 4).

Photomicrographs of longitudinal sections and cross-sections of carbon fibre posts are demonstrated in FIG. 5.

cores and prosthetic crowns [9,12]. Endodontically treatedteeth may be restored with prefabricated posts made ofstainless steel, gold, titanium, nickel-chromium-cobalt or irid-ium-platinum alloys, ceramics or custom-made cast postsproduced in the prosthetic laboratory [1,12].

For the last two years, new carbon fibre-based systemsfor restoration of lost hard tissues in endodontically treatedteeth have been available on the market as an alternativeto metallic and ceramic post and cores [2,3,8,10].

These posts contain reinforcing carbon fibres embed-ded in an epoxy resin matrix, which keeps them together.The fibres have similar physical properties as the dentin.The content of carbon fibers constitutes approximately 40-65% of the post depending on different manufacturer. Wheninserted into the root canal of the tooth they adjust to theroot's work in the alveolar bone during mastication (10).

The objective of the study

The objective of the study was SEM evaluation ofCarbonite carbon fibre post adhesion using universal resincementation system - Cement-It.

Material and methods

Fifteen human teeth - maxillary and mandibular caninesand incisors extracted for periodontal reasons and storedin 10% formalin solution - were evaluated in the study. Theteeth were divided into 3 groups, each one consisting of 5teeth, according to the size and width of the root: group Awith maxillary lateral incisors, group B with maxillary cen-tral incisors, and group C with mandibular canines. Dentalcrowns, after removing carious lesions, were cut off 1-2mmabove the cemento-enamel junction. The root canals of teethwere instrumented with K-files and next irrigated using 15%sodium versenate, 5.25% sodium hypochloride, and finallydistilled water. Teeth divided into groups were prepared withspecial fibre post reamers (Harald Nordin S.A., Switzerland)according to the canal width and adjusted to the size of thecarbon fibre post, Carbonite, (Harald Nordin s.a., Switzer-land), to be used. The root canals prepared with reamerswere irrigated once again with endondontic irrigants anddistilled water, dried and checked for post fitting in root ca-nals. Then, the dentinal surface was etched with 37% phos-phoric acid, prior to adhesion of the bonding system. Theacid was rinsed with 5ml of distilled water and root canalsdried with paper points. Resin cementation system (Pentron,Wallington, USA) consisting of one-component bondingresin, Bond 1, and a composite cement, Cement-It, wasused to fix carbon fibre posts. Root canal instrumentationand post surface preparation were carried out according tothe manufacturer's recommendations. After post insertion,each tooth was additionally light-cured for 40s to bond com-pletely the material in the root canal. The filled teeth werestored in physiological saline and incubated for 72 hours at37°C.

In order to qualitatively assess specimens they wereground to half their thickness in the labio-lingual directionand coated with gold layer of several dozen nanometers.The prepared specimens were viewed in the Hitachi S-

FIG. 2. Longitudinal section of the restored toothwith the carbon fibre post (a) and a magnifiedfragment of the post (b).

a)

b)

TABLE 1. Gap widths in restored teeth.

Gap width [µm] resin cement–carbon fibre post Dentin-resin cement

Type of the post

Mean Standard deviation

Mean Standard deviation

Large - φ 1.5 mm 0.5 1.1 0.8 1.8 Medium-φ 1.35 mm 0.5 1.0 0.7 1.2 Small - φ 1.2 mm 0.6 1.1 0.8 1.6

FIG. 3. Adequate adhesion of the post-restoredtooth system: a) resin cement-dentin, b) resincement-carbon fibre post.

a) b)

FIG. 1. Kit of carbon fibre posts for tooth

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Discussion of the results

Carbon fibre posts, Carbonite, have smooth walls andare similar in shape to a pin with a tapered end. They areavailable in 3 sizes adjusted to different sizes of the rootcanal.

Carbonite posts, in compliance with the manufacturer'scertification, contain approximately 65% of longitudinal car-bon fibres with braided plait arrangement in an epoxy resinmatrix. However, SEM investigations (FIG.5) have revealedthat fibre content is lower, and they are not arranged in theform of braided plait but parallel

In reconstruction of the endodontically compromised teethwith posts, besides the type of the material used, shape ofthe post, the amount of the removed root canal dentin andmore precisely the amount of the dentin left after canalpreparation have a significant impact on vertical fractures.The greater amount of the removed dentin whileinstrumenting the canal, the higher risk of endodonticallycompromised tooth fracture. The highest stresses occur intooth tissues prepared for a post and core but not restoredwith a post [7]. The material with higher resistance i.e., chro-mium-cobalt or chromium-nickel alloys, reduces stressesinduced in tissues of the tooth reconstructed withprosthodontic appliance. However, when we use the mate-rial whose Young module is lower than that of the dentin,then stresses generated in the root are higher than in thedentin of the healthy tooth [7]. Thus, the higher the Youngmodule in the material, the lower stresses appear in thetooth restored with the post. As regards the post shape, it isknown that optimal distribution and the least stress valuesoccur when the root segment of a post is taper-shaped andhas parallel walls in relation to root canal walls [4]. Dejakand M³otkowski in their study have revealed that stressesin the vicinity of the tooth cervix decrease along with theincrease in the thickness of the metallic post, while thinnerand longer posts, by 2/3 of root length, do not reducestresses around the dental cervix but generate higherstresses in the apical region [5]. The above considerationsindicate that the most optimal post would be the one madeof metal with a high Young module e.g., chromium-cobalt,chromium-nickel, of a medium size in relation to the root

size and taper-shaped with walls parallel to root walls asideal adhesion to the dental root surface [4, 5, 7]. Also, elas-ticity (flexibility) of the post used is as important. Carbonfibres and adhesive system have elasticity parameters closeto dentin properties [3, 10]. Since carbon fibres and the epoxyresin matrix are elastic, stresses are transmitted to the den-tal tissues.

Subsequently, the next problem arises which is associ-ated with the materials used for post cementation insidethe root. These materials are less resistant than those metalcast posts are made of. Lack of precision in fabricating apost causes production of stresses in the root while bitingand chewing, which leads to chipping off resin cement andnegatively affects resistance of the remaining tooth struc-ture [6].

The most crucial element of prosthetic restoration with apost is adhesion between the post, cement and root dentinto form an integral whole.

Failure resulting in lack of seal in teeth with composite orprosthetic crowns can be caused by iatrogenic errors dur-ing both endodontic treatment and prosthetic build-up dueto marginal leakage of the reconstructed tooth crown. Thismicroleakage is of considerable importance in necrotic teethafter the endodontic procedure, and particularly in the caseof teeth subject to root canal retreatment [11].

Due to lack of sealing, bacteria pass to hard dental tis-sues and induce secondary caries i.e., bacterial infection,subsequently leading to further complications. Microleakagepermits wet oral environment to contact with the inside ofthe already filled root canal. Such a situation can becomethe reason for failure of endodontic and prosthodontic treat-ment and makes the clinicist retreat the tooth endodonti-cally. However, retreatment is often difficult or impossibleto perform so the clinicist is forced to carry out an endodon-tic surgical procedure, which, when fails, can in consequencelead to tooth loss. That is why, sealing is of great signifi-cance in adhesive dentistry used for reconstruction of en-dodontically treated teeth.

In the teeth studied the presence of small, a few-microm-eter gaps was only sporadically observed. They occurredat the dentine/resin cement and resin cement/post inter-faces. The maximal gap size was 5 µm. Lack of sealing inroot canals can result from rapid bonding of the resin ce-ment used to fix the post. In most cases there was no dis-continuity in the specimens studied.

Thus, we can presume that the use of post and coresreinforced with carbon fibres embedded in epoxy matrix andcemented in the root canal with adhesive techniques ena-bles the tooth to maintain its durability and functioning inthe masticatory system.

It can be concluded that the applied method of non-vitaltooth restoration will be satisfactory as far as sealing andprotection against microbial penetration into the dental tis-sues are concerned.

Conclusion

Carbon fibre post system with adhesive techniques canbe an alternative to restoration of endodontically treatedteeth.

References

[1] Combe E. C. , Wstêp do materia³oznawstwa stomatologiczne-go, Warszawa 1997, Wydawnictwo Medyczne SANMEDICA.[2] da Silva R.S., de Almeida Antunes R.P., Ferraz C.C., Orsi I.A. :The effect of the use of 2% chlorhexidine gel in post-space prepa-ration on carbon fiber post retention. Oral Surg Oral Med Oral

FIG. 4. A gap in the post-restored tooth system:a) resin cement-dentin, b) resin cement-carbonfibre post.

a) b)

FIG. 5. The structure of carbon fibre posts:a) longitudinal section, b) cross-section.

a) b)

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Introduction

Several properties of cubic boron nitride (c-BN) like widebandgap width, good thermal stability, good thermal con-ductivity, or chemical and mechanical resistance make thismaterial, in combination with other wide bandgap materi-als, the potential candidate for certain microelectronics andoptoelectronics applications, particularly in the field of high-temperature and high-power devices [1-3].

Experiment

The silicon substrates used in these experiments were:p-type <100>, 4-7Wcm. Substrates were cleaned by theRCA method before the experiments. Then different dielec-tric underlayers were deposited by PECVD technique ontwo samples: sample 1 - silicon nitride, sample 2 - siliconoxynitride. After their deposition, samples were transferredto the (RF) CVD reactor and on top of them c-BN films wereproduced. Additionally, for the purpose of comparison, c-BN films were also deposited directly on silicon. The pa-rameters of the processes are presented in TABLE 1. Thethicknesses of the obtained c-BN/dielectric underlayer weremeasured elipsometrically by Gaertner L117B, l=632,4 nm.

In order to enable electrical characterisation of the ob-tained system, round dot metal electrodes (Al) were evapo-rated on top of the structures and thus metal-insulator-semi-conductor (MIS) capacitors were obtained. Subsequentlytheir capacitance-voltage (C-V) and current-voltage (I-V)characteristics were measured. C-V characteristics allowedextraction of the basic parameters (effective charge density(Qeff), flat band voltage (UFB) or mid-bands interface trapdensity (Ditmb)) of investigated systems.

At the end, adhesion of c-BN films to silicon was exam-ined, as well as the influence of the underlayer on this pa-rameter. The mechanical scriber technique was used toperform these investigations. Typical method of improvingthe adhesion is deposition of thin h-BN layer between Si

and c-BN film[4-5]. The application of Si3N4 and SiOxNy

interlayers was investigated in this work.

Results

FIG.1 shows exemplary C-V characteristics of BN filmsdirectly deposited onto silicon substrate. The curves weremeasured in two directions: from inversion to accumulation("I-A" - see FIG.1) and from accumulation to inversion ("A-I"). The hysteresis loop could be a result of big amount ofcharge that is collected in a c-BN film. Table 2 shows basicelectrophysical parameters that were extracted from C-V

Pathol Oral Radiology Endod, 2005, Vol.99, 3, 372-377.[3] De Santis R., Prisco D., Apicella A., Ambrosio L., Rengo S.,Nicolais L. : Carbon fiber post adhesion to resin luting cement inthe restoration of endodontically treated teeth. Journal of materialsscience, 2000, Apr., Vol. 11(4), 201-6.[4] Dejak B., Józefowicz W. " Wp³yw ró¿nych kszta³tów wk³adówkoronowo-korzeniowych na naprê¿enia w tkankach zêba" (Influ-ence of different designs of post and core on stresses in the tissu-es of teeth) Prot.Stomat.XLIV,1994,5,248-250.[5] Dejak B., M³otkowski A." Badanie naprê¿eñ w zêbach w zale¿-noci od wielkoci czêci korzeniowej wk³adów" (Evaluation of stres-ses in the teeth depending on size of the posts) Stomatologia Wspó³-czesna, vol.2,nr 5,1995,410-419.[6] Dejak B." Wp³yw braku przylegania wk³adu koronowo-korze-niowego do niektórych czêci korzenia na naprê¿enia wystêpuj¹-ce w strukturach odbudowanego zêba" (Influence of inaccuracy inadjustment of a post and core on the stresses in the tissues ofteeth) Prot.Stomat. 2000,L, 1,30-37.[7] Dejak. B. "Badania naprê¿eñ w zêbach odbudowanych wk³ada-mi koronowo-korzeniowymi z ró¿nych materia³ów" (Evaluation ofstresses in the teeth restored with dowels made of different mate-rials) Stomatologia Wspó³czesna, vol. 2, nr 1, 1995, 35?40.[8] Iglesia-Puig M.A., Arellano-Cabornero A. : Fiber- reinforced postand core adapted to a previous metal ceramic crown.. J ProsthetDent, 2004, vol.91, 2, 191-194.[9] Kupka T., Tanasiewicz M., Ilewicz L.: Zachowawcza odbudowaca³kowicie zniszczonej korony zêba bocznego z u¿yciem standar-dowego wk³adu koronowo-korzeniowego oraz wype³nienia kom-pozytowo- amalgamatowego (Conservative restoration of the to-tally destroyed crown of a posterior tooth with the use of a stan-dard post and combined composite - amalgam restoration) Czas.Stomat., 2001, LIV, 6, 349 - 356.[10] Lassila L.V., Tanner J., Le Bell A.M., Narva K., Vallitu P.K.:Flexural properties of fiber reinforced root canal posts, Dental Ma-terials 2004, Vol. 20, 1, 29-36.[11] Mannocci F., Ferrari M., Watson T.F. : Microleakage of endo-dontically treated teeth restored with fiber posts and composite coresafter cyclic loading : A confocal microscopic study ; J ProsthetDent , 2001, Vol.85, 3, 284-291.[12] Spiechowicz E., Protetyka Stomatologiczna, Warszawa 1992,Pañstwowy Zak³ad Wydawnictw Lekarskich.

MODIFYING ELECTROPHYSICALPROPERTIES OF SI-CBNINTERFACE BY INTRODUCTIONOF ULTRATHIN DIELECTRICLAYER

FIREK P., MROCZYÑSKI R., SZMIDT J.,BECK R.B., WERBOWY A.

INSTITUTE OF MICROELECTRONICS & OPTOELECTRONICS, WARSAW

UNIVERSITY OF TECHNOLOGY, POLAND

EMAIL: [email protected]

Abstract

This study concerns modifications of Si - c-BN in-terface (with and without dielectric underlayer). c-BNfilms produced on p-type <100> Si substrates bymeans of Radio Frequency (RF) CVD process. Sili-con nitride and oxynitride were deposited by PlasmaEnhanced Chemical Vapour Deposition technique andused as a dielectric underlayer. MIS devices were fab-ricated to allow electrical characterisation. Moreover,the influence of underlayers on adhesion of c-BN tosilicon substrate was examined.


TABLE 1. Process' parameters and thickness oflayers used in the experiments.

PECVD RF CVD Number

of sample

parameters thickness [Å] parameters thickness

[Å]

1

Underlayer - Si3N4 Power - 10W

Pressure - 45 Pa, Time - 30s,

Flows: SiH4 – 95sccm NH3 – 60sccm

38

2

Underlayer - SiOxNy

Power - 10W Pressure - 65 Pa

Time - 20s Flows:

SiH4 – 150sccm NH3 – 32sccm N2O – 16sccm

36

3 - -

Voltage - 105V Time - 45s

Pressure - 30 Pa Flow:

N2=20sccm Source of boron:

(C2H5)3B

~1500

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curve. The parameters of investigated layers are situatedin typical range for this material (depending on method andparameters of deposition [6-8]).

The current-voltage (I-V) characteristics c-BN/silicon sys-tem are presented on the FIG. 2. There are two groups of

curves. The first group represents structures, that have abreak-down for quite low voltage values and high leakageThe second group represents structures with a very goodisolating properties (see FIG.2).

Next diagram (FIG. 3) shows I-V characteristics of thestructures with ultrathin dielectric underlayer. In both casesit can be noticed that after use of ultrathin dielectricunderlayer, I-V characteristics look more reproducible.Moreover, silicon oxynitride makes the dual dielectric sys-tem more effective as an insulator - there is a visible changein a current flow.

As it was mentioned above, part of this study was theinvestigation of adhesion. In order to perform these exami-nations, the samples with and without ultrathin dielectricunderlayer were used.

FIG. 4 presents scratches on the c-BN surface whichwere made using the same weight for all investigated sam-ples. Even without any particular load (it was used only theweight of a diamond scribe holder only) there is a notice-able scratch reaching almost to the silicon substrate. Fromthese figures the following conclusion can be drown: thedielectric undelayer did not improve adhesion of c-BN filmto the silicon substrate. Further research focused on im-proving adhesion, for example high temperature annealingof dielectric film, will be necessary.

Conclusions

C-BN films were grown on the p-type <100> siliconsubstrates at the same technological process conditions. Ul-trathin dielectric layers were introduced to the dielectric/semi-conductor system. Boron nitride film was also deposited di-rectly onto silicon substrate, for comparison. Although hyster-esis loop is significant, interface state density value (in themiddle of forbidden silicon band) do not exceed 4,66e1011 forthe c-BN/silicon system. The current-voltage characteristicsbecame more repeatable and more stable after the introduc-tion of ultrathin dielectric underlayer introducing.

The c-BN/silicon oxynitride/silicon system indicates alsoa small decrease in current flow, comparing to c-BN/siliconsystem. Introducing dielectric underlayer did not improve ad-hesion of boron nitride films to the silicon substrates. Furthertechnological process will be necessary.

References

[1] R. Kirschmann (ed.), High-Temperature Electronics, IEEE Press,Piscataway, 1999.[2] P.J. Gielisse, "Wide Bandgap Materials in Future Electronic Ap-plications", IMAPS POLAND Conference 2000.[3] S. Noor Mohammad, Solid-State Electronics, 46 (2002) 203.[4] S. Kurooka, T. Ikeda, A. Tanaka, Nuclear Instruments and Me-thods in Physics Research B, 206 (2003), 1088-1091.[5] H.Walter, K. Bewilogua, A. Schutze, T. Maassen, Diamond andRelated Materials, 8 (1999), 110-113.

Parameter Value

εi 4,2

UFB - 2,44 [V]

UMB - 0,266 [V]

Qeff/q 2,41 E+11

Ditmb 4,66 E+11

TABLE 2. Basic electrophysical parameters of thec-BN layer extracted from the C-V measurements.

0,00E+00

1,00E-10

2,00E-10

3,00E-10

-6 -4 -2 0 2U [V]

C [F

]

A - I

I - A

FIG. 1. Exemplary high-frequency (1 MHz) C-Vcurves of the c-BN/silicon structure.

1,00E-14

1,00E-11

1,00E-08

1,00E-05

1,00E-02

-6 -4 -2 0

U [V]

I [A

]

FIG. 2. Current-voltage characteristics of MISstructures with c-BN produced directly on thesilicon substrate.

1,00E-14

1,00E-11

1,00E-08

1,00E-05

1,00E-02-6 -4 -2 0

U [V]

I [A

]

with SiOxNy

with Si3N4

FIG. 3. Current-voltage characteristics of MISstructures with ultrathin dielectric undelayer andc-BN.

a) b) c)

FIG. 4. Pictures of investigated layers - influenceon adhesion a. BN without underlayer; b. BN withSi3N4 underlayers; c. BN with SiOxNy underlayer.

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ticles, for example, wear debris around prosthetic joints.Macrophages are derived from circulating monocytes, mi-grating from vessels. In the presence of particles,macrophages and MNGC produce chemical mediators,known as cytokines. These can be demonstrated in situand their production can be induced in cell culture whenmacrophages are incubated with particles.

It is clear from in vitro studies that macrophages are in-duced to produce these factors when they phagocytose (en-gulf) particles. Recognition of foreign material depends ona variety of mechanisms including surface receptors for theFc component of immunoglobulin and for complement. Theparticles found adjacent to prosthetic joint components arederived mainly from the load-bearing surfaces and shed intothe synovial fluid. It is likely that particles in the body be-come rapidly coated with proteins, including albumin, globu-lins, and complement components.

An important function of some macrophages is theprocessing of ingested material and its presentation as an-tigen to lymphocytes, the specific mediator cells in immuneresponses. Antigen-presenting macrophages are found inrelation to particles in vivo, and these cells play an impor-tant part in the initiation of the process of sensitization tometal. Surface receptors and counterligands are expressedon macrophages and lymphocytes and can be detected incell culture and in tissue sections. Macrophages and MNGCalso contain nitric oxide synthase (iNOS) which gives riseto nitric oxide, a signalling molecule, and superoxidedismutase (SOD), involved in oxygen free radical produc-tion. Acid phosphatase (AcP) and non-specific esterase(NSE) play a part in the breakdown of ingested biologicalmaterial, though there is no intracellular mechanism for in-tracellular breakdown of particles of man-made materials,such as metal or polyethylene.

The particles present in tissues around joint prostheseshave been isolated and characterized. While there are oc-casional large shards visible by light microscopy, over 95%of particles are less than 1 micron (ECD) in size [1-3]. Trans-mission electron microscopy has also revealed the pres-ence in some samples of nanoparticles of metal, in the range15-20 nm. Such particles could not be taken into the cellsby the usual phagocytosis process and might bepinocytosed. The study of the effects of nanoparticles oninflammatory cells is at a preliminary phase. Hydroxyapa-tite, diamond-like carbon (nanodiamond) and metal parti-cles are being studied and results compared with those ofparticles in the micrometre range.

Materials and methods

Detailed materials and methods are not provided here inthis short review. The effect of micro- and nanoparticles onmacrophages has been studied in tissue retrieved from manafter revision surgery for prosthesis loosening and fromanimals after experimental procedures. Cell culture studiesuse primary monocytes and lymphocytes derived from pe-ripheral blood (PBM, PBL) as well as cell lines. Methods ofinvestigation include immunocytochemistry (IHC) withmonoclonal antibodies (mab), western blotting, in situhibridisation (ISH), polymerase chain reaction (PCR) andreverse transcriptase PCR (RT-PCR) as well as ELISA, bio-chemical assays (eg citrulline- arginine for iNOS) and en-zyme histochemistry (eg for AcP and NSE).


Macrophages and MNGCsExamination of tissue sections from patients undergoing

[6] J. Smidt, Chaos, Solitons & Fractals Vol. 10, No 12, pp 2099-2152, 1999.[7] A. Werbowy, P. Firek, J. Szmidt, M. Ga³¹zka, A. Olszyna, Jour-nal of Wide Bandgap Materials, SAGE Publ., vol. 9, No. 3 (2002)pp. 169-176.[8] J. Szmidt, A. Soko³owska, A. Olszyna, A. Werbowy, P. Paw³ow-ski, Diamond and Related Materials 8, (1999), 391-397.

THE EFFECT OF PARTICLES,INCLUDING NANOPARTICLES,ON MACROPHAGES IN VITROAND IN VIVO

P.A. REVELL*, H. ALTAF*, T. MCFARLANE*,D. BOCIAGA**, K. MITURA**

*EASTMAN DENTAL INSTITUTE, UCL, LONDON, ENGLAND

**TECHNICAL UNIVERSITY OF LODZ, POLAND.EMAIL: [email protected]

Abstract

Macrophages remove foreign material from thebody and are recruited to sites were there are parti-cles present. Multinucleate giant cells form by the fu-sion of macrophages. In the presence of particles,macrophages produce various chemical mediators,known as cytokines, as well as enzymes. Some ofthe cytokines are pro-inflammatory ( for example, IL1ß,IL6 and TNFa) while others promote giant cell forma-tion (GM-CSF, M-CSF, TGF). The presence of thesecellular products can be shown by examining tissuesections with immunohistochemistry and by westernblotting. The message (mRNA) for the synthesis ofthese molecules can be demonstrated by in situ hy-bridization and the polymerase chain reaction.

Macrophages process ingested material andpresent it as antigen to lymphocytes. Antigen-present-ing macrophages play an important part in the initia-tion of metal sensitization. Surface receptors and theircounterligands are expressed on macrophages andlymphocytes during antigen presentation.

The particles present in tissues around joint pros-theses have been isolated and characterized. Over95% of these are less than 1 micron (ECD) in size.Transmission electron microscopy has revealednanoparticles of metal in the range 15-20 nm. Suchparticles are too small to be phagocytosed. Hydroxya-patite, diamond-like carbon (nano-diamond) and metalparticles are being studied and results compared withthose of particles in the micrometre range. There is adifferent response to different nanoparticles.

Key words: Macrophage; lymphocyte; particles;cytokines; immunity; sensitization; nanodiamond.


Introduction

After the acute phase of inflammation, macrophages andmultinucleate giant cells (MNGC) are responsible for remov-ing foreign material, micro-organisms and dead tissue fromthe body. MNGC are formed by fusion of macrophages.Both of these cells are recruited to sites were there are par-

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how these nanoparticles enter the cell or of their effect oncell function, which has prompted our preliminary studies inthis area. A recently reported experiment showed thatnanoparticles of hydroxyapatite (nanoHA) increased theproliferation of Jurkatt T cells when cocultured with U937cells. This effect was not due to IL15 production by U937cells. More recent collaborative research has compared theeffects of microparticles of CoCr alloy (1.3-2.4µm) with threedifferent nanodiamond particles (0.15-0.81µm; 0.5-1.2µmaggregates; 0.2-0.6µm aggregates) on culture with U937cells. The expression of HLA-DR, a sign of activation, andCD80, CD86 and CD40, indicators of antigen presentation,were measured using a FACS method. Positive control wasprovided by lipopolysaccharide (LPS) and negative controlby culturing the cells in culture medium alone. CoCr, dia-mond particles (D1,DB) caused HLA-DR expression. CD86was expressed with one of these diamond particles andCoCr. There was insignificant HLA-DR or CD86 expressionthe smallest diamond (D2). The results for CD40 are shownin FIGURE 2. All values are the means with standard errors(3 replicates for each macrophage stimulant). There wasexpression of CD40 by cells incubated with CoCr and thelargest diamond particles (DB) after 24 hrs. This was re-spectively 3 and 4.5 times greater than CD40 expression inpositive controls. There was much less CD40 expression inthe case of the D1 and D2 nanodiamond particles. The re-sults are normalized to the mean value for the negativecontrols, which contained no added particles or LPS.

Conclusions

Particles in the micrometre range (0.1-2.5µm) are phago-cytosed by macrophages and cause activation of these cellson the evidence of tissue examination and cell culture stud-ies. Some macrophages fuse to form giant cells (MNGC).Macrophages and MNGC produce numerous mediators andpresent antigen to lymphocytes upon activation. Particlesin the nanometre range (<100nm) are also found inmacrophages in tissue. Relatively little is known of their ef-fects on cells but evidence is presented from preliminarystudies that macrophage activation and antigen presenta-tion is less with nanoparticles than that seen withmicroparticles.

revision surgery for aseptic loosening, shows the presenceof a cellular infiltrate composed of macrophages, MNGCsand lymphocytes [4-6], though there are also mast cells,fibroblasts and endothelial cells forming new blood vessels.This description will concern itself only with the phagocyticcells and their relationship to lymphocytes. Themacrophages and MNGCs can be labelled with mab CD68.When activated, these cells express HLA-DR and integrins(CD11a,b,c) at their surface membrane [7-9]. Double-label-ling fluorescence immunocytochemisty shows that theseactivated cells contain a number of cytokines. Such cytokineproduction can be demonstrated in functional studies ofPBM and the human monocyte/ macrophage cell line U937,using IHC and western blotting to demonstrate each cytokinein tissue and cells, ELISA to show the levels of cytokinereleased into tissue culture fluid and PCR for the mRNA ofeach cytokine in cells either in culture or in tissue. The vari-ous cytokines known to be produced on microparticle phago-cytosis in culture or in vivo are shown in FIGURE 1 [9-17].Some of these promote the inflammatory process (IL1ß,IL6, TNFa), some are anti-inflammatory (IL10), yet otherspromote MNGC or ostoeoclast formation (GM-CSF,M-CSF,TGFa -directly; IL1, TNF -indirectly).

Macrophage-lymphocyte interactionsThe presence of lymphocytes intermingled with the

macrophages and MNGCs was reported over a decade ago[18]. Accumulating evidence points to an immunologicallymediated process in the reaction to wear particles [18-21].There is clinical evidence of metal sensitization in somecases, while others with aseptic loosening show features ofa T cell mediated process on immunohistological examina-

tion and cell culture. An important function of phagocyticcells is presentation of antigen to lymphocytes. Markers ofantigen-presenting cells have been demonstrated on inter-face macrophages in aseptic loosening (RFD1, CD80,CD86) with the counterligand (CD28) found on the accom-panying T helper (CD4) lymphocytes [21-24]. Other ligandsand counterligands (HLA-DR, TCR; CD40, CD40L; ICAM,LFA-1) known to be expressed in antigen-presentation arepresent on the macrophages and lymphocytes associatedwith particles in situ [25]. Furthermore, the interaction be-tween macrophages phagocytosing particles and Tlymphocytes has been modelled in cell culture experiments.T lymphocyte activation and proliferation requires the pres-ence of IL2 or IL15. The latter is present abundantly in theparticle-related macrophage infiltrate and its production canbe stimulated on phagocytosis of particles in cultured U937cells [7, 26, 27].

Microparticles and nanoparticlesThe studies described above refer to microparticles

(>0.1µm diam). However, nanoparticles of titanium (15-20nm diam) have been noted in cells from the implant inter-face by transmission electron microscopy in our own labo-ratory and by researchers in the USA. Little is known of

FIG.1. Cytokines andother mediatorsproduced by activedmacrophages.

FIG. 2. Expression of CD 40 by U937 cells afterincubation with different particles for 24 hrs. CoCr,cobalt chromium; DB, D1, D2, diamond; positive,LPS.

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[25] Bhatt R, Saeed S, Altaf H and Revell PA. In vitro assessmentof interactions between T-cells and antigen-presenting cells (Apcs)when challenged with biomaterials: the CD40-CD40L interaction.Proc 7th World Biomaterials Congress, Sydney, Australia, 488;2004.[26] Saeed S anad Revell PA. Production and distribution of inter-leukin 15 and its receptors (IL-15R? and IL-R2ß) in the implantinterface tissues obtained during revision of failed total joint repla-cement. Int J Exp Path 82, 201-209; 2001.[27] Saeed S, Al-Saffar N and Revell PA. Expression of interleu-kin-15 (IL-15) and its receptors by U937 cells stimulated by metalwear particles retrieved from periprosthetic tissue. Proc 6th WorldBiomaterials Congress, Hawaii, 401; 2000.

THE INFLUENCE OFNANOCRYSTALLINE DIAMONDLAYERS OBTAINED BY MW/RFPECVD METHOD ON SURFACEPROPERTIES OF AISI 316 LSTEEL

TADEUSZ BLASZCZYK*, BARBARA BURNAT*, HENRYK SCHOLL*PIOTR NIEDZIELSKI** , WITOLD KACZOROWSKI**

*UNIVERSITY OF LODZ, FACULTY OF PHYSICS AND CHEMISTRY,DEPARTMENT OF GENERAL AND INORGANIC CHEMISTRY, 90-136LODZ, NARUTOWICZA 68, POLAND

**TECHNICAL UNIVERSITY OF LODZ,INSTITUTE OF MATERIALS SCIENCE,DEPARTMENT OF BIOMEDICAL ENGINEERING,90-924 LODZ, STEFANOWSKIEGO 1/15, POLAND


Abstract

Determination of corrosion parameters of AISI 316L with nanocrystalline diamond (NCD) layers depos-ited by means of new Microwave / Radio FrequencyPlasma Enhanced Chemical Vapor Deposition (MW/RF PECVD) method in testing solution 0.5 M NaClwas a basic aim of presented work. We measuredcorrosion potentials, potentiodynamic characteristics,breakdown and repassivation potentials, corrosionresistance and impedance characteristics of AISI 316L samples with- and without NCD layers. Summariz-ing obtained results it can be stated that NCD layersimprove corrosion features of AISI 316 L and that sur-face preparation techniques have insignificant influ-ence on these features.

Keywords: biomaterials, austenitic steel AISI 316L, NCD layers, electrochemistry, corrosion


Introduction

Since 1986 S. Mitura and co-workers from TechnicalUniversity in Lodz have produced nanocrystalline diamond(NCD) layers on different substrates by means of RadioFrequency Plasma Enhanced Chemical Vapor DepositionMethod (RF PECVD) [1-3]. In 2004 a new dual frequency -Microwave and Radio Frequency PECVD method was thereapplied for NCD layers deposition [4]. Dual frequency

References

[1] Yamac T, The extraction and characterisation of wear particlesfrom tissues around failed orthopaedic implants of different desi-gns PhD Thesis, University of London; 1999.[2] Kobayashi A, Bonfield W, Kadoya Y, Yamac T, Freeman MAR,Scott G and Revell PA, The size and shape of particulate polyethy-lene wear debris in total joint replacements. Proc Instn Mech En-grs [H] 211, 11-15; 1997.[3] Maloney WJ, Smith RL, Schmalzreid TP, Chiba J, Huene Dand Rubash H, Isolation and characterisation of wear particlesgenerated in patients who have had failure of hip arthroplasty wi-thout cement. J Bone Jt Surg 77A, 1301-1310; 1995.[4] Revell PA. Tissue reactions to joint prostheses and the pro-ducts of wear and corrosion. Curr Top Pathol 71, 73-101; 1982[5] Revell PA, Al-Saffar N and Kobayashi A. Biological reaction todebris in relation to joint prostheses. Proc Instn Mech Engrs 211H,187-197; 1997.[6] Al-Saffar N and Revell PA, Pathology of the Bone-Implant Inter-faces. J Long-term Effects of Medical Implants 9, 319-347; 1999[7] Revell PA and Jellie SE. Interleukin 15 production by macro-phages in the implant interface membrane of aseptically loosenedjoint replacements. J Mater Sci; Mater in Med 9, 727-730;1998.[8] Clarke SA and Revell PA. Expression of ß2 integrins at the bone/biomaterial interface. Proc Soc Biomat, San Diego, California;1998.[9] Clarke SA. Integrin expression at the bone biomaterial interfa-ce. PhD Thesis, University of London, 1999[10] Al-Saffar N and Revell PA, Pathology of the Bone-Implant In-terfaces. J Long-term Effects of Medical Implants 9, 319-347; 1999.[11] Al-Saffar N and Revell PA. Interleukin-1 production by activa-ted macrophages surrounding loosened orthopaedic implants: apotential role in osteolysis. Br J Rheumatol 33, 309-316: 1994.[12] Al-Saffar N and Revell PA. Differential expressioin of transfor-ming growth factor-a and macrophage colony-stimulating factor/colony stimulating factor-1R (c-fms) by multinucleated gian cellsinvolved in pathological bone resorption at the site of orthopaedicimplants. J Orthop Res 18, 800-807; 2000.[13] Chiba J, Rhubash HE, Kim KJ and Iwaki Y. The characteriza-tion of cytokines in the interface tissue obtained from failed ce-mentless total hip arthroplasty with and without femoral osteoly-sis. Clin Orthop 300, 304-312; 1994.[14] Al-Saffar N, Revell PA, Khwaja HA and Bonfield W. Asses-sment of the role of cytokines in bone resorption in patients withtotal hip replacement. J Mater Sci; Mater in Med 6, 762-767; 1995.[15] Al-Saffar N, Revell PA, Khwaja HA and Kadoya Y. Assessmentof the role of GM-CSF in the cellular transformation and the deve-lopment of erosive lesions around orthopaedic implants. Am J ClinPathol 105, 628-639; 1996.[16] Xu JW, Kontinnen YT, Li TF, Waris TF, Lassus J, Matucci-Cerinic M, Sorsa T and Snatavirta TS. Production of platelet-deri-ved growth factor in aseptic loosening of total hip replacement.Rheumatol Int 17, 215-221; 1998.[17] Hercus B, Saeed S and Revell PA. Expression profile of T cellassociated molecules in the interfacial tissue of aseptically loose-ned prosthetic joints. J Mater Sci: Mater Med 13, 1153-1156; 2002.[18] Lalor PA, Revell PA, Gray AB, Wright S, Railton GT and Fre-eman MAR. Sensitivity to titanium. A cause for implant failure? JBone Jt Surg 73B, 25-28; 1991.[19] Weyand CM, Geisler A, Brack ME, Bolander ME and GoronzyJJ. Oligoclonal T-cell proliferation and interferon-gamma produc-tion in periprosthetic inflammation. Lab Invest 78, 677- 685; 1998[20] Hercus B and Revell PA. Phenotypic characteristics of T lym-phocytes in the interfacial tissue of aseptically loosened prostheticjoints. J Mater Sci: Mater Med 12,1063-1067; 2001.[21] Bainbridge JA, Revell PA and Al-Saffar N. Costimulatory mo-lecule expression following exposure to orthopaedic implants weardebris. J Biomed Mater Res 54, 328-334; 2001.[22] Al-Saffar N, Revell PA and Kobayashi A. Modulation of thephenotypic and functional properties of phagocytic macrophagesby wear particles from orthopaedic implants. J Mater Sci: MaterMed 8, 641-648; 1997. [23] Altaf H, Saeed S, Bhatt R and Revell PA. The assessment ofantigen presenting cells in the bone-implant interface. Biomateria-len 4, 86; 2003.[24] Altaf H and Revell PA. The characterisation of antigen presen-ting cells in the bone implant interface & in response to biomate-rials. Proc 7th World Biomaterials Congress, Sydney, Australia,686; 2004.

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potential Ecor - 0.200V to potential in which the measuredcurrent reached to programmed value. Then the scan di-rection was inversed and the measurement was carried outto the start potential. Steps from 1 to 3 were repeated inpost-corrosion and fresh solutions.

Optical metallographic microscope was used for investi-gation of corroded samples. Scanning electron microscopyHITACHI S-3000N with an X-Ray microprobe analyzer EDXTHERMO NORAN was used for structure and elementscomposition measurements.

Results

Corrosion potentials Ecor

For each sample we measured potential E vs time t. Afinal stable potential was considered as corrosion potentialEcor. Average values of Ecor and standard deviation are pre-sented in TABLE 1.

It can be stated that Ecor values of AISI 316 L withoutNCD layers are independent from preparation method. Apotential Ecor of AISI 316 L samples with NCD layers is moreanodic in comparison with AISI 316 L samples without NCDlayers. This potential depends on preparation technique andcan be attributed with changes, which take place in struc-ture of layer's surface during NCD deposition. After anodicpolarization (designated "After corrosion") Ecor potentialsdid not monotonically change. The interpretation of observedEcor changes is difficult. The most significant is a compari-son of Ecor values in the same conditions i.e. before andafter corrosion in fresh solution. Post-corrosion solutionscan have different concentrations of corrosion products foreach examined sample, which lead to large results disper-sion (higher standard deviation). These results can be helpfulwith analysis of AISI 316 L implant's behavior in contactwith human body - products of corrosion can accumulate intissue nearby implant and cause situations close to secondperiod of presented measurement.

Breakdown potentials Eb and repassivation potentialsErep.

The preparation technique of AISI 316 L surface had anegligible influence on its potentiodynamic characteristics.FIGg.1 present example of potentiodynamic characteristicsof samples (prepared with SiC abrasive papers) with andwithout NCD layers. It is important to notice that breakdownpotentials Eb were difficult to detect from these characteris-tics - increase of measured current was not so sharp as forexample in corrosion processes of Ti in KBr solutions [13].Crevice and pitting corrosion occurred simultaneously nearrubber gasket and it is a reason of this current - potentialcharacteristic shape. That's why there is a great possibilityto make error by determining the Eb value.

FIG. 2 shows fundamental difference between featuresof both samples - pits which emerged on surface of AISI316 L without NCD developed in wide range of polarizationpotential up to potential close corrosion potential Ecor. In con-

method was in details described by L. Martinu et al. [5] fordeposition of P-SiOx films, J. E. Klemberg-Sapieha et.al.[6] for silicon nitride (P-SiN) and amorphous hydrogeneratedsilicon (a-Si:H) films, and A. Raveh et. al. [7] and P. Reinekeet. al. [8] for amorphous diamond-like carbon layers. Thismethod was used also in Technical University of Lodz forNCD layers deposition onto AISI 316 L stainless steel. AISI316 L has good mechanical properties. That's why it is oneof the most frequently used materials as bone-implantsplaced for short time [9,10]. The improvement both mechani-cal and corrosion features as result of using NCD layerswas mentioned by S. Mitura in earlier publications [11] andin details described by J. Marciniak [9]. Corrosion param-eters are different in a lot of publications. The reason lies inpreparation processes of samples' surface.

The aim of this work is to presentation of corrosion meas-urement results of austenitic AISI 316 L prepared by me-chanical polishing with abrasive paper SiC and additionallywith Al2O3, with and without NCD layers. NCD layers weredeposited by means of a new MW/RF PECVD method. Thefollowing corrosion measurement's results are presented inthis work: corrosion potential Ecor in open circuit (OCP), po-larization resistance Rp using Stern-Geary method, break-down Eb and repassivation Erep potentials and impedancecharacteristics (EIS) in 0.5 M NaCl solution.

Experimental methodology

The investigated AISI 316 L samples had cylindricalshapes with 8 mm diameter and ca. 3 mm height. The sam-ples were prepared in two different ways. One part of sam-ples was polished with abrasive paper SiC from 500 to 2000grit only, rinsed with distilled water and ethanol, and driedwith argon (99.999). The other part of samples was addi-tionally polished with Al2O3 and next rinsed with distilledwater and ethanol, and dried with argon. The surfaces ofsamples were controlled using optical metallographic mi-croscope.

On such prepared samples' surface NCD layers usingMW/RF PECVD method were deposited. Deposition proc-ess of NCD layers consisted of two steps: 1) surface etch-ing (power of MW=150 W and RF= 120 W, autopolarizationpotential Vb=-700V and duration of t=3 min,); 2) NCD lay-ers deposition (MW=150 W and RF=120 W, Vb=-700V, flowof CH4 50 sccm, and duration of t=2 min). According to abovegiven parameters can estimate a thickness of NCD layersat ca. 1µm.

Electrochemical corrosion measurements were carriedout in a glass electrolytic cell (volume ca. 2cm3) inpotentiostatic conditions using potentiostat / galvanostatPGSTAT 30 (EcoChemie AUTOLAB). Internal diameter ofrubber ring gasket was a 0.6 cm and hence the active sur-face area (in contact with solution) was ca 0.28cm2. Duringthe measurements. temperature was 250±10C and the so-lution was mechanically stirred and deoxidized with argon.Special miniature calomel electrode in saturated NaCl so-lution (standard potential E0=0.243 V) was used as refer-ence electrode - all potentials in this work are given versusthis electrode. All measurements were carried out in cycledescribed in [12]. This cycle consisted of following steps: 1)corrosion potential measurement Ecor in open circuit po-tential (OCP) method, 2) current - potential characteristicmeasurement in potential range from Ecor-0.020V toEcor+0.020V according to Stern-Geary method with scan rate0.5 mVs-1, 3) impedance characteristic measurement at Ecor

potential in frequency range from 0.04Hz to 104 Hz usingsinusoidal signal with EAC=5mV, 4) potentiodynamic char-acteristic measurement with scan rate 1 mVs-1 from start

TABLE 1. Corrosion potentials Ecor of investigatedsamples.

Before corrosion

After corrosion After corrosion

(in fresh solution) Sample Preparation

Ecor

[V] ∆Ecor[

V] Ecor

[V] ∆Ecor[

V] Ecor

[V] ∆Ecor[

V] AISI SiC -0.17 0.01 -0.24 0.12 -0.15 0.09 AISI SiC + Al2O3 -0.17 0.05 -0.31 0.12 -0.26 0.07

AISI with NCD

SiC -0.10 0.05 -0.12 0.04 -0.17 0.06

AISI with NCD

SiC + Al2O3 0.01 0.05 0.13 0.16 -0.15 0.10

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sample surface has influence on both values - Rp is higherfor samples, which are polished with Al2O3 in comparisonwith samples, which are polished with SiC. It is connectedwith surface roughness - after polishing with SiC there area large quantity of scratches on sample's surface, whichenlarge an "electrochemical" surface. This fact has high in-fluence on corrosion processes. Rp resistance of sampleswith NCD layers decreases drastically after anodic polari-zation independently of surface preparation technique.

Impedance characteristicsImpedance characteristics of AISI 316 L without and with

NCD layers after polishing with abrasive papers SiC andadditionally with Al2O3 before anodic polarization as Bodeplot shows FIG.3a. Electrical equivalent circuit used for fit-ting the experimental characteristics is presented in FIG.3b.

All presented characteristics in FIG.3a. are similar andtherefore they are not designated. Electrical equivalent cir-

trary - pits which emerged on surface of AISI 316 L withNCD layers repassivated in potential ca. 0.2 V that is morecathodic than breakdown potential Ecor. The same behavioris observed for AISI 316 L samples after polishing with Al2O3.Eb and Erep potentials are more positive for AISI 316 L withNCD layers in the range from 0.7V to ca. 1V than AISI 316Lwithout NCD. These potentials depend little on preparationtechnique (FIG.2). It means that possible differences of lay-ers' surface connected with the different preparation tech-nique, which were mentioned with corrosion potential analy-sis, have no influence on pits creation. Crevice and pittingcorrosion were detected by microscopic investigations ofsamples' surface.

Corrosion resistance Rp and corrosion current icorThe Rp resistance and corrosion current icor were calcu-

lated from Stern-Geary linear characteristics (see TABLE2).

Analyzing obtained results it can be stated that beforeanodic polarization of AISI 316 L with NCD layers the po-larization resistance Rp is 1.5÷2.0 times higher than the re-sistance Rp of the same samples without NCD. A corrosioncurrent icor behaves reversely. A preparation technique of

FIG. 1. Potentiodynamic characteristics for a) AISI316 L and b) AISI 316 L with NCD layers; samplespolishing with SiC.

a) b)

10-10

10-8

10-6

10-4

10-2

100

-0.5 0.0 0.5 1.0 1.5 2.0

E [V]

i [A cm -2 ]

FIG. 2. Breakdown Eb and repassivation Ereppotentials vs. samples preparation and NCDlayers presence.

-0.5

0.0

0.5

1.0

1.5

without NC D

(S iC )

w ithout N CD

(SiC+ Al2O3)

with NC D

(SiC)

with N CD

(SiC +Al2O 3)

E b , E rep [V] E b

E rep

TABLE 2. Polarization resistance Rp andcorrosion current icor before anodic polarization.

Sample Preparation Rp

[Ω cm2] ∆Rp

[Ω cm2] icor

[A cm-2] ∆icor

[A cm-2]

AISI

SiC

1.28⋅105 0.43⋅105 2.22⋅10-7 0.72⋅10-7

AISI

SiC + Al2O3

1.85⋅105 0.37⋅105 1.46⋅10-7 0.31⋅10-7

AISI with

NCD SiC 1.92⋅105 0.95⋅105 1.59⋅10-7 0.69⋅10-7

AISI with

NCD SiC + Al2O3 3.75⋅105 1.48⋅105 7.84⋅10-8 3.44⋅10-8

FIG. 3. Impedance characteristics of AISI 316 Lwithout and with NCD layers;a) Bode plots (see text), b) electrical equivalent.circuit.

a)

10-2 10-1 100 101 102 103 104100

101

102

103

104

105

Frequency (Hz)

|Z|

10-2 10-1 100 101 102 103 104

-90

-60

-30

0

Frequency (Hz)

theta

b) R s CPE1

R1

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cuit contains uncompensated electrolyte resistance, i.e. theresistance of electrolyte between working electrode and ref-erence one, [email protected]÷8.2 W·cm2, constant phase elementCPE1-T@(5.5÷8.8)·10-5, [email protected]÷0.94 and reactionresistance R1@(0.4÷1.9)·104 W·cm2. Constant phase elementcorresponds to the double layer capacity (CPE1-P is close1) and includes information about the surface roughness.

Conclusions

Summarizing results presented above it can be statedthat NCD layers: 1) shift a corrosion potential Ecor in morepositive values but surface preparation method has negligi-ble influence on Ecor potential; 2) shift breakdown Eb andrepassivation Erep potentials in more anodic values and de-crease a potential range in which occurs pitting corrosion;3) increase polarization resistance Rp and decrease corro-sion current icor in corrosion potential Ecor but Rp and icor

values depend on surface preparation; 4) have no influenceon impedance characteristics. In final conclusions it can bestated that NCD layers improve corrosion features of AISI316 L and that surface preparation techniques have insig-nificant influence on these features.

Acknowledgements

This work was supported by the MS&IST grant No. 3T08C 036 27.

References

[1] Mitura E., Niedzielska A., Niedzielski P., Mitura S. The proper-ties of carbon layers deposited onto titanium substrates. // Dia-mond and Related Materials - 1996. -5. - P. 998-1001.[2] Mitura S. Nanotechnology in Materials Science. - Amsterdam:Pergamon - Elsevier Science Ltd, 2000[3] Mitura S., Mitura A., Niedzielski P., Couvrat P. NanocrystallineDiamond Coatings. // Journal of Chaos, Solitons and Fractals (Spe-cial Issue) - 1999. - 10(12). - P. 2165-2177.[4] Kaczorowski W., Niedzielski P., Mitura S. Manufacture of car-bon coating for biomedical applications in a new MW/RF reactor. // Eng. of Biomaterials -2005. -43-44. - P. 28-31.[5] Martinu L., Klemberg-Sapieha J. E., Wertheimer M. R. Dual-mode microwave / radio frequency plasma deposition of dielectricthin films // Appl. Phys. Lett. - 1989. - 54. - P. 2645-2647.[6] Klemberg-Sapieha J. E., Kuttel O. M., Martinu L., WertheimerM.R. Dual microwave - R.F. plasma deposition of functional co-atings. // Thin Solid Films - 1990. - 193/194. - P. 965-972.[7] Raveh A., Martinu L., Hawthorne H.M., Wertheimer M.R. Me-chanical Properties of Dual-Frequency Plasma Deposited Diamond-like Carbon // Surf. Coat. Technol. - 1993. - 58. - P. 45-55.[8] Reinke P., Klemberg-Sapieha J.E., Martinu L. Effect of Amor-phous Carbon Layers on the Growth of Diamond in Dual-Frequen-cy Plasma // J. Appl. Phys. - 1994. - 76. - P. 5754-5759.[9] Marciniak J. Biomateria³y. - Gliwice: Wydawnictwo Politechnikil¹skiej, 2002 P. 493.[10] Laskawiec J., Michalik R. Zagadnienia teoretyczne i aplikacyj-ne w implantach. - Gliwice: Wydawnictwo Politechniki l¹skiej, 2002P. 170.[11] Couvrat P., Denis M., Langer M., Mitura S., Niedzielski P.,Marciniak J. The corrosion tests of amorphous carbon coatingsdeposited by r.f. dense plasma onto steel with different chromiumcontents. // Diamond and Related Materials - 1995. - 4. - P. 1251.[12] Boguslawski G., Blaszczyk T., Scholl H. Electrochemical cor-rosion of Ti6Al4V alloy with nanocrystalline diamond coatings. //Eng. of Biomaterials - 2004. - 38-42. - P. 160-163.[13] Scholl H., Blaszczyk T., Niedzielski P., Gralewski J. Biomate-rials in nanoelectrochemistry - corrosion investigations of Titaniumand Titanium with NCD layers. // Eng. of Biomaterials - 2004. - 35-36. - P. 45-53.

CORROSIVE FEATURES OF TiWITH NANOCRYSTALLINEDIAMOND LAYERS OBTAINED BYMEANS RADIO FREQUENCY ANDMICROWAVE / RADIOFREQUENCY PLASMA CHEMICALVAPOR DEPOSITION METHODS

BARBARA BURNAT*, WITOLD KACZOROWSKI**,GRZEGORZ BOGUSLAWSKI**, TADEUSZ BLASZCZYK*,HENRYK SCHOLL*

*UNIVERSITY OF LODZ, FACULTY OF PHYSICS AND CHEMISTRY,DEPARTMENT OF GENERAL AND INORGANIC CHEMISTRY,90-136 LODZ, NARUTOWICZA 68**TECHNICAL UNIVERSITY OF LODZ,INSTITUTE OF MATERIALS SCIENCE,DEPARTMENT OF BIOMEDICAL ENGINEERING,90-924 LODZ, STEFANOWSKIEGO 1/15E-MAIL: [email protected]

Abstract

A new dual-mode microwave / radio frequency(MW/RF) plasma reactor for deposition ofnanocrystalline diamond (NCD) coatings has beendeveloped in Technical University of Lodz. In this workwe present the results of investigations concerninginfluence of NCD layers deposition method on corro-sive features of Ti in Tyrode's solution. NCD layerswere produced by means of Radio Frequency and Mi-crowave / Radio Frequency Plasma Chemical VaporDeposition (RF PCVD and MW/RF PCVD).Electrochemical investigations show that both NCDcoatings improve some corrosive features of Ti. How-ever obtained results show that pitting corrosion didnot occur on Ti/NCD RF samples, but it occur on Ti/NCD MW/RF despite of thicker NCD layers.

Keywords: Ti; nanocrystalline diamond (NCD);NCD deposition methods; RF PCVD; MW/RF PCVD;electrochemical measurements; corrosion parameters.

[Engineering of Biomaterials, 56-57 ,(2006),34-37

Introduction

Ti and its alloys play an important role in medical appli-cations as implants [1]. Materials used in human body, asmedical implants, must be characterized by: goodbiocompatibility, chemical stability, biostability, good adhe-sion and excellent mechanical characteristics [2]. In orderto enhance mechanical properties, corrosion resistance andbiocompatibility of biomaterials a deposition of different car-bon coatings is used. Diamond-like carbon (DLC) andnanocrystalline diamond (NCD) are the most often usedcarbon coatings. DLC films contain 80% sp3-bonded car-bon [3,4]. NCD coatings, as Mitura reported in [5], have athickness of about 0.5-1 µm and are composed of 97% dia-mond. One of the latest works about Microwave PlasmaChemical Vapor Deposition (MPCVD) technique signalizesa possibility of producing a new form of diamond film calledultrananocrystalline diamond (UNCD) which consist of crys-talline grains of 95% sp3-bonded carbon that are 3-5 nm insize [4]. DLC, NCD and UNCD layers are produced in dif-ferent chemical vapor deposition processes: Radio Fre-

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scope. Surface structure and elements composition analy-sis of samples after corrosion process were performed us-ing scanning electron microscopy with X-ray analysis (SEM-EDX) method.


Electrochemical measurementsValues of open circuit potential E vs. time t were col-

lected for each sample. Time of registration was from 2000still 6000s. Stabilized electrode potential was established ascorrosion potential Ecorr. Averaged values and standard de-viations of Ecorr are presented in TABLE 2. Potentiodynamiccharacteristics dependence of current density j=I/A (I - meas-ured current [A], A - sample surface [cm2]) versus polariza-tion potential E [V] are presented in FIG.1. Breakdown po-tential Eb and repassivation potential Erep values obtainedfrom these characteristics are also presented in TABLE 2.In case of Ti electrodes with NCD layers deposited by RFPCVD method pitting corrosion did not occur, and thereforeEb and Erep values were impossible to detect.

Analyzing data presented in TABLE 2 it can be statedthat NCD layers cause increase of corrosion potential Ecorrform -0.383 V to 0.165 V (ca. 0.45 V) in case of RF PCVDand form -0.383 V to 0.065 V (ca. 0.55 V) in case of MW/RFPCVD deposition methods. In case of Ti without NCD andTi with NCD layers deposited using plasma vapor deposi-tion method with radio frequency (called Ti/NCD RF) therewas no breakdown in Tyrode's solution. Oxidation peakcurrent was observed in potential range 1-3 V on the ob-tained potentiodynamic characteristics for Ti/NCD RF. Thisoxidation peak was joined with intensive gas bubbling onsample surface, and it can be attributed to presence ofgraphitic (sp2) material on deposited NCD layers [13]. ForTi samples with NCD layers deposited using dual frequencyplasma vapor deposition method (called Ti/NCD MW/RF)breakdown potential Eb was close to 3.4 V. Repassivation

quency Plasma Chemical Vapor Deposition (RF PCVD) [5],Microwave Plasma Chemical Vapor Deposition (MPCVD)[4] and Microwave / Radio Frequency Plasma ChemicalVapor Deposition (MW/RF PCVD) [6-8].

In Technical University of Lodz are available RF PCVDand MW/RF PCVD methods for NCD layers deposition. Theaim of this study was to compare an influence of these depo-sition methods on corrosive features of Ti in Tyrode's solu-tion, especially an oxidation of sp2-bonded carbon, break-down potential, repassivation potential, polarization resist-ance, corrosion rate and type of corrosion. Obtained differ-ences in corrosive features may be joined with changing ofsurface layers different for used deposition techniques

.Experimental

All measurements were done using cylindrically shapedsamples of Ti (99.99 - Aldrich) with a diameter of 6.35 mm.Preparation of Ti electrodes consisted of sequential wetpolishing with 1000 and 2000 grit SiC paper, polishing withdiamond gel 1 µm and chemical etching in Kroll's solution(HF:HNO3:H2O in volume ratio 1:3:5 respectively). Finally,the samples were rinsed with distilled water and dried inargon. The surface appearance was verified using opticalmetallographic microscope. Such prepared Ti samples werecovered by NCD using two different methods: RF PCVDand MW/RF PCVD. RF generator was connected to work-ing electrode with Ti samples. MW power was appliedthrough a quartz tube mounted in opposite to working elec-trode [8]. The main parameters of NCD deposition proc-esses are shown in TABLE 1.

According to parameters given in TABLE 1 a thicknessof NCD layers can be estimated at ca. 0.5 µm for RF PCVDand even four-times higher for MW/RF PCVD.

Electrochemical measurements were carried out in aglass electrolytic cell with a volume of ca. 2 cm3 [9]. All cor-rosion measurements were carried out in a typical three-electrode system. Calomel electrode in saturated NaCl so-lution was used as a reference electrode. Tyrode's solution(0.8 g NaCl, 0.02 g CaCl2, 0.02 g KCl, 0.1 g NaHCO3, 0.1 gD-glucose, 0.1 MgCl2, 0.005 g NaH2PO4 and H2O in 100cm3 solution) [10] was prepared from chemical reagentsPOCh S.A. (Polish Chemical Reagents) and Aldrich - withpurity "for analysis" - without additional purification. Follow-ing electrochemical methods were used in corrosion meas-urements according to [11]: open-circuit potential (OCP) forcorrosion potential Ecorr detection, Stern-Geary's method forpolarization resistance Rp and corrosion rate CR detection,potentiodynamic curves for breakdown potential Eb andrepassivation potential Erep detection and electrochemicalimpedance spectroscopy (EIS) which allowed to determineproperties of phase boundary electrolyte solution / sample[12].

The surface appearance before and after the corrosionprocess was verified using optical metallographic micro-

TABLE 1. The main parameters of NCD depositionprocesses.

Parameters RF PCVD MW/RF PCVD Gas Ar Ar

Bias voltage -800 V -700 V RF power 2.5 kW 320 W MW power - 150 W

Ion etching

Time of etching 2 min 10 min Gas CH4 CH4

Bias voltage -800 V -700 V RF power 2.5 kW 500 W MW power - 150 W

Gas stream velocity 25 sccm 20 sccm

Deposition of NCD layers

Time of deposition 10 min 12 min

TABLE 2. Corrosion, breakdown andrepassivation potentials.

Sample Ecorr [V] Eb [V] Erep [V]

Ti -0.383±0.026 no exist no exist

Ti/NCD (RF PCVD) 0.165±0.001 no exist no exist

Ti/NCD (MW/RF PCVD)

0.065±0.040 3.38±0.33 3.22±0.28

FIG. 1. Potentiodynamic characteristics ofinvestigated electrodes in Tyrode's solution.

-2E -03

0E+00

2E-03

4E-03

6E-03

8E-03

1E-02

-2 0 2 4 6 8 10

E [V]

j[A /cm 2]

Ti

Ti/NCD RF

Ti/NCD MW/RF

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potential Erep was ca. 3.2 V for these samples. Oxidationpeak was not observed on these samples. That's why thepresence of graphitic (sp2) material on surface of Ti/NCDMW/RF may be negligible.

Polarization resistance Rp and corrosion rate CR werecalculated from Stern-Geary's characteristics usingCorrView program. The Stern-Geary's characteristics wereregistered with scan rate 0.5 mV/s in potential range fromEcorr -20 mV to Ecorr +20 mV. Averaged values of these pa-rameters are presented in TABLE 3.

Analyzing data presented in TABLE 3 it can be statedthat NCD layers deposition on Ti causes more than ten-times increasing of Rp values. Corrosion rates for Ti withNCD layers, independent of deposition method, are orderof magnitude smaller than for Ti without NCD.

Impedance characteristics EIS were registered at Ecorrpotential in wide frequency range from 10 kHz to 40 mHz,with a harmonic signal EAC =5 mV. Examples of character-istics for investigated samples and electrical equivalent cir-cuit fitting obtained experimental data are presented in FIG.2.

The circuit was the same for all investigated samples. Itcontained uncompensated electrolyte resistor Rs, two iden-tical branches CPE1 || R1 and CPE2 || R2 connected inseries. The first branch CPE1 || R1 describes impedancecharacteristics in high frequency range, while the secondbranch CPE2 || R2 describes them in low frequency range.CPE1-T element corresponds to differential double layercapacity of phase boundary solution / sample, while CPE1-P values corresponds to surface roughness. Resistance R1describes corrosion processes. R1 value significantly in-creases after NCD layers deposition, what can be joinedwith decreasing of corrosion reaction rate. Simultaneouslydecreases differential double layer capacity (CPE1-T).Physicochemical meaning of CPE2 and R2 is equivocal -these elements may correspond to phase boundary tita-nium oxide / titanium features [14].

Microscopic measurements - surface structure and el-ements composition analysis

SEM picture of Ti without NCD and optical microscopesimages for Ti with NCD layers are presented in FIG.3.Changes caused by pitting corrosion on Ti/NCD MW/RFare shown in FIG. 4. Elements composition for three pointsof corroded surface marked on FIG.4b are presented inTABLE 5.

On Ti surface without NCD layers and after NCD layersdeposition the crystallites of the substrate are clearly visible(FIG. 3). NCD layers deposited using RF PCVD methodchange the sample color form metallic-silver to yellow (FIG.3b), while layers deposited by means MW/RF PCVD methodgive blue color (FIG. 3c). FIG.4a shows that corrosion proc-esses for Ti/NCD MW/RF take place on whole crystallitessurface with preferable orientation (areas out of focus). Thiseffect is confirmed by SEM picture (FIG. 4b). Elements com-position data from TABLE 5 show that Ti, O and C are presentin any point of this surface. Moreover the presence of otherelements such as Na, Mg, P, Cl and Ca was found in points1 and 3 and it may be joined with corrosion processes inTyrode's solution. Smooth region with point 2 is a region ofcrystallites which did not corrode. Making a comparison of Ccontents in analyzed points it can be found that in points 1and 3 the contents of C are unexpectedly higher than in point2. This fact can be explain by the appearance of C from glu-cose existing in Tyrode's solution.

Summary and conclusions

Electrochemical investigations show that both NCD coat-ings improve some corrosive features of Ti. In case of Ti

TABLE 3. Averaged values of corrosion rate CRand polarization resistance Rp..

Sample CR [mmPY] Rp [Mohm·cm2] Ti (5.65±0.46)⋅10-5 4.0±0.3

Ti/NCD (RF PCVD) (3.49±0.18)⋅10-6 64.7±3.6 Ti/NCD (MW/RF PCVD) (4.18±0.66)⋅10-6 54.6±8.6

0 100000 200000

-400000

-300000

-200000

-100000

0

Z'

Z''

10-2 10-1 100 101 102 103 10410010

1

102

103

104

105

106

Frequency (Hz)

|Z|

10-2 10-1 100 101 102 103 104

-90

-60

-30

0

Frequency (Hz)

theta

b

FIG. 2. Nyquist (a) and Bode (b) plots for Ti (o), Ti/NCD RF (´) and Ti/NCD MW/RF (+); electricalequivalent circuit (c).

Sample Rs [ohm·cm2]

R1 [ohm·cm2]

CPE1-T CPE1-P R2 [ohm·cm2]

CPE2-T CPE2-P

Ti 14.4 64 8.53⋅10-4 0.657 5.28⋅105 1.77⋅10-5 0.928

Ti/NCD RF 12.1 2498 5.63⋅10-5 0.897 5.11⋅106 8.37⋅10-6 0.886

Ti/NCD MW/RF 17.3 7246 2.96⋅10-5 0.821 4.48⋅106 1.06⋅10-5 0.829

TABLE 4. Elements' values of electrical equivalentcircuit.

a) b) c)

FIG. 3. SEM picture of Ti without NCD (a), opticalmicroscope images of Ti/NCD RF (b) and Ti/NCDMW/RF (c).

a) b)

FIG. 4. Pitting corrosion on Ti/NCD MW/RF: opticalmicroscope image (a), SEM picture (b).

Point 1 Point 2 Point 3 Atom % El. Wt. % Atom % El. Wt. % Atom % El. Wt. %

Ti 36.88 60.53 87.08 95.50 36.75 60.47 C 5.02 2.06 2.58 0.71 6.46 2.67 O 48.45 26.57 10.34 3.79 46.99 25.82 Na 1.65 1.30 - - 1.65 1.30 Mg 0.84 0.70 - - 0.86 0.72 P 0.90 0.95 - - 1.18 1.25 Cl 4.56 5.54 - - 4.00 4.87 Ca 1.71 2.34 - - 2.11 2.91

TABLE 5. SEM-EDX element composition of Ti/NCD MW/RF surface after corrosion.

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PROPERTIES OF NiTi - SHAPEMEMORY ALLOY AFTERMODIFICATION BY RF PCVDMETHOD

M.CZERNIAK-RECZULSKA*, P.COUVRAT**, J.GRABACZYK*,P.NIEDZIELSKI**BIOMEDICAL ENGINEERING DIVISION,INSTITUTE OF MATERIALS SCIENCE AND ENGINEERING,TECHNICAL UNIVERSITY OF LODZ, POLAND

**MATERIALS DEPARTMENT,ECOLE CATHOLIQUE D'ARTS ET METIERS, LYON, FRANCE

E-MAIL :[email protected]

Abstract

The DLC (diamond-like carbon) and NCD(nanocrystalline diamond) layers coat made implantsof medical steel 316 L, titanium and titanium alloys[1]. These layers have excellent properties such as:high hardness, good biocompatibility to various typesof cells, good adhesion to implants [2], wheres im-plants with diamond layer have good corrosion resist-ance in body fluids. Result received for these materi-als are encourage to modification other materials forexample shape memory alloy NiTi. Nitinol is often usedmaterial in interventional cardiology, orthodontics andurology [3]. Shape memory alloy charackterizes ofreturn to designed shape, superelasticity,thermomechanical behavior [3]. This phenomenonsare proceeded thanks to the martensite transforma-tion. Modification in high temperature perhaps causefailure martensite transformation which influence onthe material properties change.

Key words: nitinol, diamond layer, RF PCVDmethod


Introduction

Nitinol - equatomic shape memory alloy is often usedmaterial to production of vascular stents, filters, implants inorthopedics and orthodontics [3]. NiTi is characterized byan unique combination of properties, superelasticity,thermomechanical behavior, low density and shapememory. These are very favourable phenomenons takinginto account the difference of size of blood-vessels wherethe implants are predicted to be introduced. Phenomenonsin NiTi are proceeded thanks to martensitc transformation.The term martensitic phase transformation describes theformation during cooling or during loading with an externalstress of the austenite high temperature phase [9]. In thisphenomenon occurs atoms re-organise. This transforma-tion dose not change the chemical composition. Results ofthis transformation are new crystal lattice.

All materials, which are implanted, should fulfill manyfactors, they could not cause allergic response or inflam-matory reaction. They must exhibit biocompatibility - theability of the human body to endure the implants withoutdestruction of the tissue. They must have a specific systemof mechanical properties - good adhesion, good corrosionresistance in body fluids.

Although studies have demonstrated the good corrosionresistance and biocompatibility of Nitinol [4], but the highnickel content at this alloy (54,5 to 57% weight) makes pos-

with NCD layers the shift of corrosion potential was observedin more positive values. Moreover the corrosion rates of Tiwith both NCD layers are order of magnitude smaller thanfor Ti without NCD. The both NCD coatings have compara-ble values of corrosion rate and polarization resistance. In-vestigated samples with different NCD coatings have simi-lar impedance characteristics and the same equivalent elec-trical circuit.

Obtained electrochemical results show different corrosivefeatures of NCD layers deposited on Ti using two differenttechniques - pitting corrosion did not occur on Ti/NCD RFsamples, but it occur on Ti/NCD MW/RF despite of thickerNCD layers. Microscopic investigations made for Ti/NCD MW/RF show that localized corrosion process is joined with sur-face microstructure - pitting corrosion take place on wholecrystallites surface with preferable orientation. These differ-ences in corrosive features may be joined with changing ofsurface layers different for used deposition techniques. Inelectrochemical aspect the new method MW/RF PCVD (de-spite of existing breakdown at 3.4V) is better in comparisonwith RF PCVD, because there is no anodic peak in potentialrange 1-3V. Therefore it can be supposed that the presenceof graphitic (sp2) material on NCD layers deposited by MW/RF PCVD method is smaller.

Summarizing obtained results can be stated that MW/RF PCVD technique requires subsequent improvement ofthe main parameters of NCD deposition processes on Ti sothat the breakdown will be eliminate or the breakdown po-tential will be shifted to maximum value.

References

[1] Marciniak J. Biomaterialy. - Gliwice: Wydawnictwo Politechnikil¹skiej, 2002[2] Long M., Rack H.J. Titanium alloys in total joint replacement - amaterials science perspective // Biomaterials - 1998. - 19. - P. 1621-1639.[3] Friedmann T.A., Sullivan J.P., Knapp J.A., Tallant D.R., Follsta-edt D.M. Medlin D.L., Mirkarimi P.B. Thick stress-free amorphous-tetrahedral carbon films with hardness near that of diamond // Appl.Phys. Lett. - 1997. - 71. - P. 3820-3822.[4] Carlise J.A., Auciello O. Ultracrystalline Diamond. Propertiesand Applications in Biomedical Devices // Interface - 2003. - 12. -P. 28-31.[5] Mitura S. Nanotechnology in Materials Science. - Amsterdam:Pergamon - Elsevier Science Ltd, 2000[6] Raveh A., Martinu L., Hawthorne H.M., Wertheimer M.R. Me-chanical Properties of Dual-Frequency Plasma Deposited Diamond-like Carbon // Surf. Coat. Technol. - 1993. - 58. - P. 45-55.[7] Reinke P., Klemberg-Sapieha J.E., Martinu L. Effect of Amor-phous Carbon Layers on the Growth of Diamond in Dual-Frequen-cy Plasma // J. Appl. Phys. - 1994. - 76. - P. 5754-5759.[8] Kaczorowski W., Niedzielski P., Mitura S. Manufacture of car-bon coatings for biomedical applications in a new MW/RF reactor // Eng. of Biomaterials - 2005. - 43-44. - P. 28-31.[9] Boguslawski G., Blaszczyk T., Scholl H. Electrochemical corro-sion of Ti6Al4V alloy with nanocrystalline diamond coatings // Eng.of Biomaterials - 2004. - 38-42. - P. 160-163.[10] Bell E., Wingate R.J.T., Eddison M.,Toole L. Segmental iden-tity and cerebellar granule cell induction in rhombomere 1. - BMCBiology - 2004. - 2 (14). - ISSN 1741-7007.[11] ASTM G 102-89 (Reapproved 2004) Standard Practice forCalculation of Corrosion Rates and Related Information from Elec-trochemical Measurements.[12] Bard A.J. Electrochemical methods. Fundamentals and appli-cations. - John Wiley & Sons, Inc., New York, 1980[13] Hian L.C., Grehan K.J., Compton R.G., Foord J.S., Marken F.Nanodiamond thin films on titanium substrates // J.Electrochem.Soc.- 2003. - 150. N 1. - P. E59-E63.[14] Kolman D.G., Scully J.R. Electrochemistry and passivity of aTi-15Mo-3Nb-3Al beta-titanium alloy in ambient temperature aqu-eous chloride solutions // J.Electrochem.Soc. - 1993. - 140. - P.2771-2779.

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sible dissolution by corrosion and it still remains a concern.The corrosion ions caused failure cells and allergic response.In this emergency implants is rejected.

Due to assure biocompatibility implants on NiTi investiga-tions over modification NiTi [3] are conducted. Our investiga-tion qualifies NiTi properties after coated it them withnanocrystalline diamond layer manufactured by RF PCVD(Radio Frequency Plasma Chemical Vapour Deposition)method [5]. Idea of this method has consists in the processof activated of dense plasma in methane in a radio frequencyfiled 13,56 MHz. Manufacturing process of diamond layersconsisted of two stages: ion etching of surface NiTi and dia-mond layer deposition on this surface.

NCD layer manufactured by RF PCVD is biocompatibility[6]. It does not cause allergic reactions and it does not con-tribute inflammation. Implants with NCD layer have goodcorrosion resistance in body fluids.

Materials and methods

In these tests were used NiTi samples delivered byMemory Metalle (Germany) such as:- disks (diameter = 4,6 mm and thickness - 2 mm)- ribbons (thickness - 0,63 mm, width -3,34 mm and lenght- 40 mm). Surface ribbons preparation dark grey oxide.

On this samples were manufactured diamond layer byRFPCVD (Radio Frequency Plasma Chemical VapourDeposition) method [5]. Parameters of coating processshows TABLE 1. Before the RF PCVD process sampleswere mechanical polished and ultrasonic cleaned.

Samples' surface and structure after test was observed onthe metallographic microscope and scanning electron micro-scope SEM. The microhardness of pure NiTi and NiTi with dia-mond layer were also examined. It was bending strength meas-urement pure NiTi and NiTi coated diamond layer.


Before and after the NiTi samples coating by diamondlayer X-ray analysis were made samples surface were ob-served by SEM.

FIG. 1a. shows results of clear disks analysis and in thetable is range of content of elemenets. It can be seen thatNi and Ti are principals elements of this alloy. Surface ofNiTi disk shows FIGURE 1b.

FIG. 2a. shows results of clear ribbons analysis and inthe table is range of content of elemenets. It can be seenthat Ni and Ti and O are principals elements of this alloy.Surface of NiTi ribbon shows FIGURE 2b.

FIG. 3a. shows analysis results of disks with diamondlayer and in the table is range of content of elemenets. Sur-face of NiTi disks with diamond layer shows FIGURE 3b.

FIG. 4a. shows analysis results of ribbon with diamond layerand in the table is range of content of elemenets. Surface ofNiTi riboon with diamond layer shows figure 4b. It can be seenthat diamond layers is constant and uniformity.NiTi structure

Structure of NiTi disks and ribbons was observed bymetallographic microscope.

The view of pure NiTi disk structure shows FIG.5a. On

the FIG. 5b was showed structure of NiTi disk after RF PCVDprocess. It can be seen that diamond layer on the NiTi rib-bon is constant.

The view of NiTi disk structure pure ribbon shows FIG.6a.On the FIG.6b was showed structure of NiTi ribbon after RFPCVD process.

Pictures show that structure of disks and ribbon aftercoating changed.Microhardness

Was mesurement before and after RF PCVD processmicrohardness of NiTi.. Microhardness was made on the 6clear NiTi samples and 6 samples with diamond layer. Re-sults of these tests are shown in TABLE 2. It can be seenthat microhardness after coating changed. During the RFPCVD process followed strengthen material.Bending

Clear NiTi ribbon and NiTi ribbon with diamond layer werebending. FIG.7,8 show results of these test. It can be seenthat NiTi samples after RF PCVD process did not return tooriginal shape. Structrue of NiTi change. RF PCVD proc-ess makes the plasticity properties lower.Differential Scaning Calorimetry

On the clear NiTi and NiTi with diamond layer were madedifferential scanning calorimetry (DSC). Measurements weremade in range temperatures from -50 to 250oC. The flowgas in the time test was 50ml/min. FIG.9 shows curve DSCTABLE 1. Parameters of RF PCVD process.

ETCHING COATING Potential

[V] Time

t [min]

Potential [V]

Time t

[min]

Flow of gas process

[cm3/min] NiTi disks 840-860 5 - 8 700-750 6 - 9 20-30 NiTi ribbons 700-740 4 - 7 680-720 3 - 5 20-30

FIG. 1. Clear NiTi disks :a) results of X-Rayanalysis, b) SEM view.

a) b)

FIG. 2. Clear NiTi ribbon: a) results of X-Rayanalysis, b) SEM view.

b) a)

FIG. 3. NiTi disk with diamond layer: a)result ofX-Ray analysis, b) SEM view.

a) b)

FIG. 4. NiTi ribbon with diamond layer: a)result ofX-Ray analysis, b) SEM view.

b) a)

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References[1] B.P. McNamara, H. Murphy, M.M. Morshed: "Adhesion proper-ties of diamond-like coated orthopedic biomaterials"; Diamond andRelated Materials: 10 2001 1098-1102.[2] G. Heinrich, B. Rinne, R. Thull, S.M. Rosiwal, R.F. Singer, "Cha-racterization of CVD diamond-coated titanium base compounds forbiomedical applications," Biomed. Tech. (Berl.) 43(1998):382-383(Suppl).[3] C.D.J.Barras and K.A.Myers "Nitinol-its use in vascular surgeryand other application"; Eur Jvasc Endovasc Surg 19,564-569 (2000).[4] P. Rocher, L. El Medawar, J.-C. Hornez, M. Traisnel, J. Breme,H.F. Hildebrand: "Biocorrosion and cytocompatibility assessment ofNiTi shape memory alloys" ; Scripta Materialia 50 (2004) 255-260[5] S.Mitura, A.Mitura, P.Niedzielski, P.Couvrat: "Nanocrystalline dia-mond coatings" Biomaterials: Volume: 17, Issue:6, 1996, pp. 587-595[6] Bakowicz K., Mitura S.: "Biocompatybility of NCD";Journal ofWide Bandgap Materials,Vol.9, No.4 (2002)261-2711.[7] Duerig T., Peton A.Stockel D. "An overview of nitinol medicalapplications" Materials Science and Engineering Volume:273-275,December 15, 1999, pp. 149-160.[8] M.F.Chen, X.J.Yang, R.X.Hu, Z.D.Cui, H.C.Man: "Bioactive NiTishape memory alloy used as bone bonding implants" ;MaterialsScience and Engineering C 24-20.[9] http://herkules.oulu.fi

clear NiTi under heating and cooling. It can be seen thattemperatures transformation Ap upon heating to amount10oC and temperature transformation Mp upon cooling toamount 20oC.

FIG.10 shows NiTi curve DSC with diamond layer underheating and cooling. It can be seen that temperature trans-formation Ap upon heating to amount 30oC and tempera-ture transformation Mp upon cooling to amount 10oC.

Conclusions

Investigations results show that modification by RadioFrequncy Plasma Chemical Deposition method NiTi doesnot satisfy expectations. Modification NiTi caused lower me-chanical properties instead high them. The SEM images ofdiamond layer on the NiTi surface shows that layer is homo-geneous and coats surface of NiTi samples very good butstructure tests of NiTi shows that RF PCVD process causedmaterial's change. High temperature during the process coat-ing that's the problem, which destroits shape memory. phe-nomenon. Test DCS showed that RF PCVD process changestransformation temperatures upon heating an upon cooling.This is very unfavourably phenomenos. Material after RFPCVD does not good shape memory and superelasticity.

FIG. 7. Clear NiTi afterbending.

FIG. 8. NiTi withdiamond layer after

FIG. 9. Curve DSC clear NiTi.

FIG. 10. NiTi DSC curve after RF PCVD process.

TABLE 2. Microhardness NiTi- average for 6samples.

Microhardness NiTi– average for 6 samples Before RF PCVD After RF PCVD

291 HV 370 HV

b) a)

FIG. 5. View of NiTi disk structure- metallographicmicroscope - magnification 275x: a)clear NiTi, b)NiTi with NCD.

FIG. 6. View of NiTi ribbon with diamond layerstructure - metallographic microscope -275x:a)clear ribbon, b) ribbon with NCD.

a) b)

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BIOMATERIA£Y W LECZENIUPOURAZOWYCH UBYTKÓWNERWÓW OBWODOWYCH PRZEGL¥D METOD IMATERIA£ÓW

DARIUSZ SZAREK**, W£ODZIMIERZ JARMUNDOWICZ*,ANETA FR¥CZEK***, STANIS£AW B£A¯EWICZ***

*KATEDRA I KLINIKA NEUROCHIRURGII AKADEMII MEDYCZNEJ,UL. TRAUGUTTA 166, WROC£AW

**ZAK£AD CHORÓB UK£ADU NERWOWEGO,AKADEMIA MEDYCZNA WE WROC£AWIU,UL. TRAUGUTTA 116, WROC£AW

***AGH - AKADEMIA GÓRNICZO-HUTNICZA,KATEDRA BIOMATERIA£ÓW,AL. MICKIEWICZA 30, 30-059 KRAKÓW


Streszczenie

Niniejsza praca stanowi przegl¹d literaturowy me-tod, sposobów, a tak¿e materia³ów stosowanych orazbêd¹cych sferze badañ do konstrukcji protez do re-generacji obwodowego uk³adu nerwowego. Zawierarównie¿ opis anatomicznych i fizjologicznych proce-sów przebiegaj¹cych podczas regeneracji nerwów, atak¿e zestawienie ich w³asnoci biomechanicznych.

S³owa kluiczowe: regeneracja nerwów, technikaoperacyjna, biomateria³y


Wstêp

Urazowe uszkodzenia nerwów obwodowych s¹ powa¿-nym problemem zarówno z punktu widzenia klinicznego jaki spo³ecznego. Stosowane obecnie metody leczenia, w tymoperacyjnego, pozwalaj¹ na uzyskanie wzglêdnie dobrych,lecz zwykle nie do koñca zadowalaj¹cych wyników lecze-nia. Leczenie jest ¿mudne i czêsto obarczone konieczno-ci¹ pobrania innego zdrowego nerwu skórnego dla napra-wy uszkodzenia. Urazowe uszkodzenia obwodowego uk³a-du nerwowego s¹ przyczyn¹ du¿ej iloci interwencji chirur-gicznych.

W 1995 roku w Stanach Zjednoczonych przeprowadzo-no ponad 50,000 operacji z powodu urazowych uszkodzeñnerwów obwodowych [1]. Liczba zabiegów wykonywanychw kilku orodkach w Polsce wynosi ponad 100 rocznie wka¿dym z nich [2]. Urazy z regu³y dotycz¹ osób w dwóchgrupach wiekowych: m³odzie¿ do 15 lat oraz osób w wieku30-50 lat [3]. Prowadzi to do znacznej absencji choroboweja niekiedy stanowi przyczynê powa¿nego kalectwa.

Jedn¹ z g³ównych trudnoci w operacyjnym leczeniu ura-zowych uszkodzeñ nerwów obwodowych jest wykonaniezespolenia przerwanego nerwu w przypadkach z du¿ymubytkiem pomiêdzy przeciêtymi koñcami [3,4]. Trójwymia-rowe materia³y u¿ywane obecnie jako skafoldy dla regene-racji tkanek mog¹ zast¹piæ obecnie stosowan¹ w takichprzypadkach klasyczn¹ metodê, jak¹ jest zespolenia kiku-tów nerwu z zastosowaniem allograftów lub autografówpobranych nerwów skórnych [5]. Metoda klasyczna jestzwi¹zana z szeregiem ograniczeñ takich jak dostêpnoæ id³ugoæ pobranego nerwu celem przeszczepienia, odner-wienie pola skórnego zaopatrywanego przez pobrany nerw,drugie miejsce operacyjne, ryzyko infekcji w miejscu po-

BIOMATERIALS IN THETREATMENT OF PERIPHERALNERVE INJURIES AN OVERVIEWOF METHODS AND MATERIALS

DARIUSZ SZAREK**, W£ODZIMIERZ JARMUNDOWICZ*,ANETA FR¥CZEK***, STANIS£AW B£A¯EWICZ***

*MEDICAL UNIVERSITY OF WROCLAW,DEPARTMENT OF NEUROSURGERY,UL. TRAUGUTTA 166, WROCLAW

**MEDICAL UNIVERSITY OF WROCLAW,INSTITUTE OF NERVOUS SYSTEM DISEASE,UL. TRAUGUTTA 116, WROCLAW

***AGH-UST, DEPARTMENT OF BIOMATERIALS,AL. MICKIEWICZA 30, 30-059 CRACOW


Abstract

The work presents the state of the art in the area ofmethods and materials used in peripheral nervetreatmend. Anatomical and physiological aspects ofperipheral nerves their biomechanical properties andtheir treatment are presented.

Keywords: nerve regeneration, operation proce-dure, biomaterials


Introduction

Peripheral nerve injuries are serious clinical and socialproblems. Current applied treatment methods, includingoperative, ones give relatively good, however not fullysatisfacting effects. Treatment is long lasting and often har-vesting of healthy cutaneus nerve is necessary. Traumaticperipheral nervous system injuries are the reason of greatnumber of surgical interventions. In 1995, there were morethan 50,000 peripheral nerve repair procedures performedin USA [1]. Number of surgical procedures performed inseveral centers in Poland is over 100 a year in every one ofthem [2]. Patients are typically in two age groups: youngpeople till the age of 15 and middle-aged between 30 and50 [3]. It causes significant disease absence and even maylead to serious disability.

One of the major problems in surgical treatment of theperipheral nerve injuries is ends coaptation in the case oflarge loss of nerve tissue [3,4]. Three dimensional materi-als in the form of scaffolds for tissue regeneration may re-place currently applied classical technique, namely nervecoaptation with the use of cutaneous nerve allo and auto-graphs [5]. There are many disadvantages of classic methodsuch as limited availability and length of donor nerve tis-sue, skin denervation in area related to harvested nerve,second operative location, and risk of infection in the regionof nerve harvesting [6]. Several types of materials have beenproposed as peripheral nerve substitutes, for example: syn-thetic materials such as silicon, polylactic acid andpolyglicolic acid, natural polymers such as chitosan,alginates, collagen, laminin, fibronectin, and others [7].

Anatomical and physiological aspectsof peripheral nerve regeneration

Peripheral nerve consists of bunches of nerve fibers con

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brania nerwu [6]. Szereg materia³ów mo¿e mieæ potencjal-ne zastosowanie dla uzupe³nienia ubytków nerwów, np.:materia³y syntetyczne takie jak silikon, poliglikolid, polilak-tyd, naturalne polimery jak chitozan, alginiany, kolagen, la-minina oraz fibronektyna i inne [7].

Anatomiczne i fizjologiczne aspektyregeneracji nerwów obwodowych

Nerw obwodowy zbudowany jest z grup w³ókien nerwo-wych po³¹czonych warstwami os³onek ³¹cznotkankowych.W³ókno nerwowe tworzy wypustka komórki nerwowej po-kryta os³onk¹ mielinow¹ wytworzon¹ przez specjalne ko-mórki zwane komórkami Schwanna.

Nerwy, ze wzglêdu na charakter przewodzonych bod-ców nerwowych, dziel¹ siê na ruchowe - przewodz¹ce im-pulsy odrodkowe i czuciowe - przewodz¹ce impulsy do-rodkowe z receptorów czuciowych. Ponadto w obrêbienerwów przebiegaj¹ w³ókna uk³adu autonomicznego. Wiêk-szoæ nerwów ma charakter mieszany, przewodz¹ w³óknanerwowe wszystkich typów.

Komórki nerwowe, których wypustki tworz¹ nerwy ob-wodowe, le¿¹ w obrêbie rogów przednich rdzenia krêgo-wego oraz w zwojach miêdzykrêgowych. Wytwarzane przeznie w³ókna nerwowe po opuszczeniu kana³u krêgowegogrupuj¹ siê tworz¹c nerwy rdzeniowe.

W pocz¹tkowym przebiegu nerwy te z regu³y ³¹cz¹ siêtworz¹c sploty, w obrêbie których dochodzi do wymianyw³ókien nerwowych pomiêdzy poszczególnymi pniami ner-wowymi. Ze splotów wychodz¹ nerwy, które unerwiaj¹ w³a-ciwe dla nich miênie, skórê, ciêgna, stawy. Nerwy ob-wodowe maj¹ kszta³t walca, przebiegaj¹ czêsto wspólnie znaczyniami krwiononymi.

W³ókna nerwowe grupuj¹ siê tworz¹c pêczki. Pêczkipokryte s¹ os³onk¹ ³¹cznotkankow¹ - perineurium. Prze-strzeñ pomiêdzy poszczególnymi w³óknami wype³niona jestlun¹ tkank¹ - endoneurium. Pêczki stanowi¹ wewnêtrzn¹makroskopow¹ architekturê nerwu, przebiegaj¹ spiralnie iw sposób sfa³dowany. Taki uk³ad pozwala na swobodnewyd³u¿enie siê nerwu w czasie jego rozci¹gania [8]. W ob-rêbie jednego nerwu przebiega z regu³y kilka pêczków.Pokryte s¹ one wspólna os³onk¹ - epineurium, z któr¹ s¹luno zwi¹zane. Stanowi ona zewnêtrzn¹ os³onê nerwu.Poredniczy ona miêdzy wewnêtrznymi strukturami nerwu,a rodowiskiem zewnêtrznym, chroni jego wnêtrze przedurazami mechanicznymi, przewodzi wiêksz¹ czêæ naprê-¿eñ podczas naci¹gania nerwu [8].

Dla prawid³owego funkcjonowania nerwu konieczna jestci¹g³oæ anatomiczna w³ókien nerwowych oraz sprawne po-³¹czenie synaptyczne w³ókna nerwowego z jego efektorem.Wyró¿niane s¹ trzy g³ówne stopnie uszkodzenia nerwu:· Neurapraxis - przejciowe zablokowanie funkcji nerwuspowodowane np. jego uciniêciem i niedokrwieniem· Aksonotmesis - przerwanie w³ókien nerwowych bez uszko-dzenia os³onek ³¹cznotkankowych· Neurotmesis - ca³kowite przeciêcie nerwu.

W stopniu pierwszym i drugim regeneracja zachodzispontanicznie z dobrym rokowaniem dla wyników leczenia.W stopniu trzecim niemo¿liwa jest spontaniczna regenera-cja, dla uzyskania powrotu funkcji nerwu konieczna jest in-terwencja chirurgiczna i zespolenie przeciêtych kikutównerwu.

Regeneracja nerwu ró¿ni siê zasadniczo od procesówgojenia siê charakterystycznych dla wszystkich innych tka-nek. Dla przywrócenia funkcji nerwukonieczna jest regene-racja ("odroniêcie") w³ókna nerwowego od miejsca uszko-dzenia a¿ do efektora i odbudowaniez nim po³¹czenia sy-naptycznego.

nected by connective tissue-sheets. Nerve fiber is createdby nerve cell process covered with myelin sheet producedby special cells called Schwann cells.

Nerves, depending on the type of conducted nerve im-pulses, are divided into motional - conducting anterogradeimpulses, sensational - conducting retrograde impulses fromsensory receptors. A nerve also consists of fibers of auto-nomic system. Most of the nerves are mixed, they consistof nerve fibers of all types.

Nerve cells creating processes for peripheral nervesfibers are located in the front horns of spinal cord or in in-tervertebral ganglions. Nerve fibers after leaving vertebralcanal group and create spinal nerves. Proximal parts ofnerves connect and build the structures called nervousplexus, where fibers exchange between particular nervestakes place. Nerves leaving these structures innervate char-acteristic muscles, skin, tendons and joints. Peripheralnerves are cylinder in shape, they often run together withblood vessels.

Nerve fibers group into structures called fascicles. Fas-cicles are covered with connective tissue sheath - perineu-rium. Space between the fibers is filled with lose connec-tive tissue - endoneurium. Fascicles are internal macro-scopic nerve architecture with spiral and fold molding. Sucha shape enables the nerve elongation during its stretching[8]. In one nerve there are usually few fascicles. They arecovered with common sheath - epineurium, loosely con-nected with. It is an external nerve cover. It mediates be-tween internal nerve structures and external environment,protects nerve internal structures from mechanical injuryand conducts biggest part of tension during nerve tighten-ing [8].

Normal nerve functioning requires anatomic integrity ofnerve fibers and functioning synaptic connection of nervefiber with its efector. There are three main types of nerveinjuries:· Neurapraxis - transient block of nerve function inflicted byfor example pressure and nerve blood flow dysfunction· Aksonotmesis - nerve fibers disruption without damage ofconnective tissue sheaths· Neurotmesis - complete nerve cut

At the first and the second stage of injury nerve regen-eration occurs spontaneously with good treatment progno-sis. At the third stage of injury spontaneous regeneration isimpossible, surgical intervention and nerve end coaptationis necessary for nerve function restoration.

Nerve regeneration greatly differs from healing processescharacteristic for all other tissues. For nerve function resto-ration nerve fibers regeneration ("regrowth in") is neces-sary from injury site to efector and rebuild of synaptic con-nection.

Nerve regeneration process runs in few phases. Duringthe first phase multiple pathophysiologic events occur de-scribed as Wallerian degeneration. This process is con-nected with myelin sheaths and nerve fibers break up thatgreatly depends on cells called macrophages. These cellsbesides phagocytic properties play an important role in sup-porting nerve fibers reconstruction process, called regen-eration. They produce multiple substances called cytokines.Cytokines, for example REG 1, stimulate Schwann cellsproliferation and also production of neurotrofic substancessuch like NGF (Nerve Growth Factor). These substanceswith retrograde axonal transport reach cell body and stimu-late expression of genes responsible for protein productionfor axonal regeneration. Schwann cells build characteristicbands or tubes of Büngner, within of which regrowing axonsgrowths in. [9,10].

Without anatomic nerve fiber reconstruction from injury

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to target organ, synaptic connection reconstruction and re-construction of myelin sheath nerve function restoration isimpossible. Actually applied treatment methods, classicaland experimental utilize this process to achieve an optimalnerve regeneration effect. Nerve stumps reconnection cre-ates conditions for regrowing axons from the proximal stumpto growth into the distal stump. In cases of great nerve tis-sue loss reconstruction with nerve autografts is necessary.Recently, for this purpose synthetic materials are being ex-plored.

Biomechanical properties of peripheralnerves

A peripheral nerve consists of nerve fibers and connec-tive tissue of different mechanical properties. Because ofthe arrangement of connective tissue and the tubular con-figuration of nerve fibers, the nerves are anisotropic andalmost transversely isotropic. It is difficult to estimate theresponse of nerves to external forces due to their small sizeand complicated architecture. The main peripheral nervecomponent responsible for the elasticity and tensile strengthof an intact nerve is epineurium [11]. The epineurial sheathdoes not rupture at one given point in the nerve, but ratheralong the nerve over some distance. Therefore, stretch in-juries to peripheral nerve may not be localized phenom-enon [12]. The materials used for supporting peripheralnerve regeneration have to have sufficient tensile strengthand mechanical toughness to withstand in vivo mechanicalforces. Investigation of tensile properties is a requisite stepin the further development of peripheral nerve substitutes[7]. The mechanical parameters like ultimate stress andstrain, ultimate elongation, Young's modulus, work to fail-ure, viscoelastic behavior are necessary to evaluate suchcharacteristics of any material designed for implantation inpatients.

For rabbit tibial nerve, the tensile strength and ultimatestrain are found to be 11,7±0,7 MPa and 38,5±2,0%, re-spectively. The strain at the "elastic limit" ranged from 8%to 20%, and the maximal strain at failure was approximately30%. These ranges of variation were thought to be due tothe nonhomogenous structure of nerve trunks, which con-sist of a complex variety of elements with different strengthand elasticity [12]. The rabbit tibial nerve has an ultimateelongation of 16,3±0,7mm and ultimate load of 9,52±0,47N.For human ulnar nerves the ultimate load is reported to be65 to 155 N human median nerve 73 to 220N [12,13].

Peripheral nerves exhibit highly nonlinear stress-strainbehavior. The nerve may stretch up to 15% strain underminimal stress of internal structures.

These mechanical properties of peripheral nerve aredetermined by special interal nerve architecture that ena-bles an optimal tensile stress load. Inside epineurium fasci-cles run freely and are loosely connected with it. They runin a spiral, wavy way along to longitudinal nerve axis. Thus,there is an excess of length of fascicles in relation to epineu-rium. During nerve stretching tensile stress is transferredby epineurium and fascicles straightening. Further stretch-ing may cause epi, perineurium and nerve fibers disruption[8,12]. These data are similar to in vivo observations of in-traneural blood flow in the rabbit tibial nerve. During gradualstretching venular blood flow significantly decreases whennerve is stretched to 8% beyond in vivo length. Completeintraneural ischemia was induced at 15% beyond in vivolength [1,11,12].

The estimated mean Young's modulus of the rabbit sci-atic nerves in the transverse direction was 66.9±8.0 kPa,and the longitudinal direction was 580±150kPa [7,11]. The

Proces regeneracji nerwu przebiega w kilku fazach. Wpierwszej fazie dochodzi do szeregu zjawisk patofizjologicz-nych okrelanych jako degeneracja Wallera. U podstawytych zjawisk le¿y rozpad os³onek mielinowych oraz wypu-stek nerwowych, w których istotn¹ rolê odgrywaj¹ komórkizwane makrofagami. Komórki te oprócz w³aciwoci ¿er-nych odgrywaj¹ równie¿ wa¿n¹ rolê we wspomaganiu pro-cesu odbudowy w³ókien nerwowych, który okrelamy rege-neracj¹. Wytwarzaj¹ one szereg substancji zwanych cyto-kinami. Cytokiny, np. cytokina REG 1, stymuluj¹ komórkiSchwanna do proliferacji, jak równie¿ do produkcji substancjineurotroficznych takich jak NGF (Nerve Growth Factor).Substancje te drog¹ wstecznego transportu aksonalnegodocieraj¹ do cia³a komórkowego i pobudzaj¹ ekspresjê ge-nów odpowiedzialnych za produkcjê bia³ek koniecznych dlaregeneracji aksonu. W tym czasie komórki Schwanna wy-twarzaj¹ charakterystyczne pasma lub rurki Büngnera, wktóre wrastaj¹ odrastaj¹ce aksony. Proces regeneracji koñ-czy siê momentem wytworzenia po³¹czeñ synaptycznychoraz os³onek mielinowych wokó³ odrastaj¹cych aksonów[9,10].

Bez anatomicznego odbudowania w³ókna nerwowego odmiejsca urazowego przeciêcia do narz¹du docelowego,wytworzenia z nim funkcjonalnej synapsy i odbudowaniaos³onki mielinowej niemo¿liwy jest powrót funkcji nerwu.Stosowane metody leczenia, zarówno klasyczne jak i eks-perymentalne d¹¿¹ do wykorzystania powy¿szego proce-su celem uzyskania jak najskuteczniejszego wyniku rege-neracji nerwu. Zespala siê kikuty nerwu koniec do koñca,co stwarza warunki by odrastaj¹ce w³ókna nerwowe z kiku-ta proksymalnego mog³y wrosn¹æ w kikut dystalny. W przy-padkach urazów, w których dochodzi do ubytku nerwu ko-nieczne jest wype³nienie ubytku przeszczepami nerwów. Wostatnich latach próbuje siê wykorzystywaæ w tym celu innemateria³y pochodzenia sztucznego.

W³asnoci biomechaniczne nerwówobwodowych

Nerwy obwodowe zbudowane s¹ z w³ókien nerwowychoraz os³onek nerwowych zbudowanych z tkanki ³¹cznej oró¿nych w³aciwociach mechanicznych. Ze wzglêdu narozmieszczenie tkanki ³¹cznej oraz cylindrycznej konfigu-racji w³ókien nerwowych, nerwy obwodowe posiadaj¹ w³a-snoci anizotropowe. W przypadku nerwów trudno jest osza-cowaæ ich odpowied na dzia³anie si³ zewnêtrznych zewzglêdu na ich skomplikowan¹ budowê. G³ównym elemen-tem sk³adowym nerwów obwodowych odpowiedzialnym zaich elastycznoæ oraz wytrzyma³oæ na rozci¹ganie jestepineurium [11]. Warstwy epineurium nie ulegaj¹ przerwa-niu w jednym, konkretnym punkcie na powierzchni nerwów,ale wzd³u¿ nerwu na pewnym jego odcinku. Dlatego te¿uszkodzenie nerwów obwodowych na skutek rozci¹ganianie jest zjawiskiem zlokalizowanym [12]. Materia³y, któreznajduj¹ zastosowanie w regeneracji nerwów obwodowychmusz¹ charakteryzowaæ siê dostateczn¹ wytrzyma³oci¹ narozci¹ganie oraz odpornoci¹ na obci¹¿enia dynamicznetak, aby zdolne by³y przeciwdzia³aæ si³om dzia³aj¹cym wrodowisku "in vivo". Badania nad w³asnociami mechanicz-nymi s¹ niezbêdnym krokiem w dalszym rozwoju materia-³ów stosowanych dla regeneracji nerwów obwodowych [7].W³aciwoci mechaniczne takie jak naprê¿enie i odkszta³-cenie graniczne, wyd³u¿enie graniczne, modu³ Younga, pra-ca zniszczenia s¹ niezbêdne do dokonania charakterystykimateria³ów przeznaczonych na implanty.

Dla nerwów piszczelowych królika wytrzyma³oæ na roz-ci¹ganie oraz odkszta³cenie graniczne wynosi odpowied-nio 11,7±0,7MPa i 38,5±2,0%. Osi¹gniêcie "górnej granicy

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mechanical properties of peripheral nerve are important forprotection of nerve fascicles and the integrity of their physi-ological functions. Connective tissue of nerves has an im-portant function in maintaining specific environment of theendoneural space by acting as a diffusion barrier againstseveral macromolecular substances. Changes in its diffu-sion properties or structural damage caused by stretchingmay lead to chronic or even permanent impairment of nervefunction [12].

Treatment procedures

In the cases of nerve transection surgical interventionfor anatomical nerve stumps coaptation is needed. Actu-ally, a method of the first choice is end to end coaptationwith few stitches binding epineurium.

Tension after nerve coaptation greatly deteriorates re-generation effect, therefore nerve injuries with nerve tissueloss require tissue defect supplementation. [9,14]. Nerveautografting is the most common surgical procedure cur-rently used for repair of nerve injuries with nerve tissueloss defects. Bridging the defect with an autologous donornerve is associated with several disadvantages, includingan extra incision for harvesting of a healthy sensory nerveultimately resulting in a sensory dysfunctions, risk of painfulneurinoma formation [9,14,15,16,17].

For these reasons processes regulating nerve regenera-tion and alternative to the autologus nerve grafts artificialmaterials are still being investigated.

Requirements for artificial nerve guidesimplants

Ideal implant for nerve substitute should have the follow-ing characteristics:1. biocompatibility;2. bioresorbability;3. potential for stimulating nerve regeneration;4. material with an ability for l incorporation of nerve growthfactors;5. should have an appropriate mechanical properties de-scribed by Young's module;6. easy for intraoperative handling;7. inexpensive [18,19].

Regeneration process in nerve tube implantOne of the main research directions in peripheral nerve

regeneration are experiments with membranes creating iso-lated environment for regenerating nerve tissue. Classicmodel of nerve tissue loss regeneration relates to emptytube-shape implants. The tube implant connects nerve endsand creates between them isolated environment for freetissue reconstruction.

Regeneration process in empty tube implant occurs inseveral subsequenty stages. Within the first hours after im-plantation implant's lumen tills-in with acellular fluid origi-nating from nerve stumps inserted in tube. It is rich innerothrophic and nerve regeneration stimulating agents. Inthe next stage, fluid is exchanged with loose, acellular ex-tracellular matrix formed mainly by fibrin. After 7 days thefibrin is longitudinally organized lengthwise long implant'saxis creating bridge between the nerve stumps, with hour-glass-shape with the narrowest part located closer to distalnerve stump. Nerve bridge diameter is much thinner thantube [20]. Longitudinal fiber organization is regularly disor-ganized by arch-like bending of fibers creating in transver-sal section the characteristic arches with bases directed tothe implants center [21].

elastycznoci" nerwów ma miejsce przy odkszta³ceniu od8% do 20%, a maksymalne odkszta³cenie do zniszczeniaoszacowane zosta³o na oko³o 30%. Rozbie¿noci w warto-ciach odkszta³cenia mog¹ byæ spowodowane brakiemhomogenicznoci w strukturze pnia nerwu, który zawieraz³o¿one sk³adniki charakteryzuj¹ce siê odmienn¹ elastycz-noci¹ oraz wytrzyma³oci¹ [12]. Dla nerwów piszczelowychkrólika wyd³u¿enie graniczne wynosi 16,3±0,7mm, a obci¹-¿enie graniczne 9,52±0,47N. Dla ludzkich nerwów ³okcio-wych obci¹¿enie graniczne jest oszacowane pomiêdzy 65N,a 155N, a dla nerwów porodkowych od 73 do 220N [12,13].

Nerwy obwodowe wykazuj¹ siln¹ nielinearn¹ charakte-rystykê naprê¿enie-odkszta³cenie. Nerw mo¿e byæ rozci¹-gany do 15% wartoci odkszta³cenia przy minimalnym na-prê¿eniu struktur wewnêtrznych.

Powy¿sze w³aciwoci mechaniczne nerwu s¹ determi-nowane specjaln¹ budow¹ wewnêtrzn¹ nerwu, która za-pewnia najoptymalniejsze przenoszenie naprê¿eñ. W ob-rêbie epineurium pêczki s¹ u³o¿one swobodnie i luno znim zwi¹zane. Ich przebieg jest pofa³dowany w stosunkudo osi d³ugiej nerwu. Daje to nadmiar d³ugoci pêczków wstosunku do d³ugoci epineurium. Podczas rozci¹ganianerwu dochodzi do powstawania naprê¿eñ, które w wiêk-szoci s¹ przenoszone na epineurium i prostowania pêcz-ków. Dalsze rozci¹ganie mo¿e spowodowaæ przerwanieos³onek epi i perineurium oraz rozerwanie w³ókien nerwo-wych [8,12]. Wyniki tych badañ potwierdzaj¹ obserwacje invivo przep³ywu krwi w naczyniach nerwu. Ukrwienie nerwukrólika znacz¹co spada przy zwiêkszeniu przy¿yciowym d³u-goci o 8%. Kompletne zatrzymanie kr¹¿enia w nerwie na-stêpuje przy rozci¹gniêciu powy¿ej 15% [1,11,12].

Oszacowana wartoæ modu³u Younga dla nerwów kul-szowych królika w kierunku poprzecznym wynosi66.9±8.0kPa, natomiast w kierunku pod³u¿nym 580±150kPa[7,11]. Znajomoæ parametrów mechanicznych nerwów ob-wodowych jest konieczna z punktu widzenia ochrony pêcz-ków nerwów, a tak¿e zachowania ich prawid³owej funkcjifizjologicznych. Tkanka ³¹czna spe³nia równie¿ bardzo wa¿-n¹ funkcjê w utrzymaniu odpowiedniego rodowiska w ob-rêbie ródnerwia poprzez utrzymanie bariery dyfuzji dla ró¿-norodnych makrocz¹steczek. Zmiany w parametrach dyfu-zji oraz uszkodzenia struktury powsta³e na skutek naprê-¿eñ rozci¹gaj¹cych, mog¹ powodowaæ d³ugotrwa³e, a na-wet sta³e, upoledzenie funkcji nerwu [12].

Metody leczenia

W przypadku przeciêcia nerwu konieczna jest interwen-cja chirurgiczna celem odtworzenia anatomicznej ³¹czno-ci miêdzy kikutami przerwanego nerwu. Stosowan¹ obec-nie metod¹ z wyboru jest zespolenie operacyjne nerwu ko-niec do koñca.

Zespolenie nerwu pod napiêciem znacz¹co pogarszawynik regeneracji, dlatego w urazach przebiegaj¹cych zubytkiem nerwu konieczne jest jego uzupe³nienie [9,14].Autoprzeszczepy nerwów s¹ obecnie najbardziej powszech-n¹ procedur¹ operacyjn¹ stosowan¹ przy naprawie ubytkunerwów. Mostowanie defektu nerwu za pomoc¹ autogenicz-nego nerwu dawcy ma szereg stron ujemnych, takich jakdodatkowe miejsce operacyjne, pobranie zdrowego nerwu,którego rezultatem s¹ zaburzenia czucia, ryzyko powsta-nia bolesnego nerwiaka [9,14,15,16,17].

Dlatego d¹¿y siê do lepszego poznania procesów steru-j¹cych regeneracj¹ nerwów oraz znalezienia materia³ówalternatywnych dla przeszczepów autogennych.

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Matrix is then colonized by cells, initially by extra neuralelements extraneural. Between 4 and 7 day, fibroblast-likecells originating from perineurium appear. These cells typi-cally first cover internal wall of the implant, followed by colo-nization at lumen. Fibroblasts are followed by Schwann cellsforming bunds of Bunger and successively blood vessels.During acellular matrix formation Schwann cells in nervestumps arouse and start to proliferate, more effective in distalthan in proximal stump. Since 4-7 day Schwann cells startto migrate into tube lumen, beginning from distal stump[20,21,22]. They arrange longitudinally along an axis cre-ated by fibrin fibers arrangement. The most effective cellu-lar reconstruction proceeds along the tube walls and sub-sequently concentrically to the implant centre. Axons growthinto the implant, from proximal side, begins from the end offirst week [20]. It is accompanied by Schwann cells fromproximal stump that are creating axons myelin sheet as itelongates. During axon regeneration Schwann cells in thefront or behind of growth cone are found. However, it isknown, that Schwann cells are capable to colonize implantindependently of contact with axon [20,22,23]. Regenera-tion process greatly enhances from 9 day after tube im-plantation [21]. After connection of proximal and distal re-generation parts (for implants 10 mm long it takes about16-17 day, while for 25 mm long 21 day) digit-like proc-esses take place with transiently disorganizing local longi-tudinal orientation [15,21]. After 7 days axons penetratedistal part of implant and elongate using support providedby Schwann cells originating from distal stump. The distalstump is reached after 21-28 days [20,21,24]. Growth ofaxons in distal part of implant is now oriented by longitudi-nal Schwann cell orientation. Direct contact of distalSchwann cells with axon stops their proliferation. If distaland proximal aspects of regeneration process are not con-nected, Schwann cells from distal stump and axons fromproximal stump, after short migration (about 4-5 mm), usu-ally stop to migrate. Schwann cells create cup-like struc-tures covering distal stump [10,15,21,25,26]. Myelinizationprocess between 14 - 36 day and advances from proximalto distal stump [20,22]. Simultaneously extracellular matrixcreated by fibroblasts maturates providing mechanical sup-port for growing tissue. Excessive connective tissue or evencicatrice formation takes place in areas related to foreignbody such as silicon or fibers of non-absorbable treads.Connective tissue greatly disturbs orientation of fibrin fila-ments and hampers cells and axons migration [21]. In latephases of regeneration number of counted axons in distalstump is greater than in proximal one. It is explained by thefact that the growth cones produce few independently re-generating processes that extend into the distal stump. Thisprocess increases chances of successful regeneration forparticular single axon [21,22]. During the second week bloodvessels start to grow into the implant, both from proximaland both distal stump. Vessels follow the front of migratingcells and axons. By the end of third week the vessels fromstumps meet in the central regeneration zone nourishingabout 10 mm tissue section [20,21]. Elimination of bloodflow from nerve stumps makes impossible nerve tissue re-generation [23,27].

Regenerated nerve fibers are thinner; both axons andmyelin sheaths [10,15,20,21,22,25,26,28]. During tissuematuration number of axons decreases while diameter ofmyelin sheahs increases [22,29,30]. Some implants, likesilicone, show tendency to stimulate parietal connective tis-sue creation. This tissue tightens and narrows the nervespace inducting degenerative processes in regeneratednerve tissue. Nerve fibers are damaged showing morpho-logical tissue image comparable with multiple crush injury[22]. This process greatly differs from aging process of re-

Wymagania stawiane przed sztucznymiimplantami nerwowymi

Idealny implant, który mo¿e byæ u¿yty do uzupe³nieniaubytków nerwów obwodowych powinien charakteryzowaæsiê nastêpuj¹cymi w³asnociami:1. biozgodnoæ;2. bioresorbowalnoæ;3. stymulacja regeneracji nerwu4. zdolny do generowania grup funkcyjnych na swojej po-wierzchni, pozwalaj¹cych na inkorporacjê czynników mo-dyfikuj¹cych regeneracjê w³ókien nerwowych5. o zbli¿onych do nerwów obwodowych w³aciwociachmechanicznych okrelanych przez modu³ Younga;6. porêcznoæ chirurgiczna;7. tani; [18,19]

Procesy regeneracji zachodz¹ce w implancieG³ównym nurtem badañ prowadzonych w celu zast¹pie-

nia przeszczepów z nerwów obwodowych materia³emsztucznym s¹ projekty zwi¹zane z budow¹ membran two-rz¹cych odizolowane rodowisko dla regeneruj¹cej tkankinerwu. Modelowym przyk³adem pozwalaj¹cym na pozna-nie sekwencji zdarzeñ maj¹cych miejsce podczas regene-racji/rekonstrukcji przez organizm ubytku nerwu s¹ bada-nia z zastosowaniem pustych implantów w kszta³cie rurki.£¹czy ona kikuty nerwu zapewniaj¹c pomiêdzy nimi odizo-lowane rodowisko, w którym mo¿liwa jest swobodna od-budowa tkanki.

Procesy regeneracji nerwu zachodz¹ce w pustym wsz-czepie na bazie rurki przebiegaj¹ w kilku nastêpuj¹cych posobie etapach. W ci¹gu kilku godzin po implantacji wiat³oimplantu wype³nia siê p³ynem bêd¹cym przes¹czem z ki-kutów nerwu. Jest on bogaty w czynniki neurotroficzne istymuluj¹ce regeneracjê nerwów. W nastêpnym etapie p³ynwewn¹trz implantu wype³nienia siê lun¹, bezkomórkow¹macierz¹ pozakomórkow¹ zbudowan¹ g³ównie z fibryny. Do7 doby po zabiegu w³óknik organizuje siê linijnie wzd³u¿ osid³ugiej implantu tworz¹c wewn¹trz rurki pomost ³¹cz¹cy ki-kuty nerwu. Jego kszta³t przypomina rozci¹gniêt¹ klepsy-drê z przesuniêtym najwê¿szym punktem w kierunku kiku-ta dystalnego. rednica pomostu jest z regu³y cieñsza odrednicy rurki. W obrêbie macierzy widoczne s¹ pojedyn-cze erytrocyty, których iloæ spada ku rodkowi implantu[20].Uk³ad linijny wzd³u¿ osi d³ugiej rurki jest regularnie zabu-rzony przez ³ukowate ugiêcie siê w³ókien tworz¹c na prze-kroju poprzecznym charakterystyczne ³uki podstaw¹ skie-rowane do rodka implantu [21]

Na tak przygotowane rodowisko wrastaj¹ komórki, po-cz¹tkowo s¹ to elementy pozanerwowe. Jako pierwsze,oko³o 4-7 dnia, pojawiaj¹ siê fibroblasto-podobne komórkiwywodz¹ce siê z unerwia. Zwykle pokrywaj¹ one najpierwzewnêtrzn¹ cianê regeneratu, a nastêpnie wype³niaj¹cetak¿e wiat³o rurki. Za nimi postêpuj¹ komórki Schwanna wformie ³añcuchów oraz kolejno naczynia. W czasie formo-wania siê bezkomórkowej macierzy wewn¹trz implantu do-chodzi do wzbudzenia i namna¿ania siê komórek Schwan-na w kikutach nerwu, w wiêkszym stopniu w kikucie dystal-nym ni¿ proksymalnym. Pocz¹wszy od oko³o 4-7 doby za-czynaj¹ one migrowaæ w wiat³o implantu, najpierw od stro-ny kikuta dystalnego[20,21,22]. Uk³adaj¹ siê linijnie, wzd³u¿osi okrelonej przez uk³ad w³ókien fibryny. Proces odbudo-wy komórkowej zachodzi najszybciej wzd³u¿ cian, a na-stêpnie postêpuje koncentrycznie do rodka implantu. Odstrony proksymalnej w wiat³o implantu wrastaj¹ aksony,które pojawiaj¹ siê pod koniec pierwszego tygodnia[20].Towarzysz¹ im komórki Schwanna z kikuta proksymalne-go buduj¹ce os³onkê w miarê wyd³u¿ania siê aksonu. Ko-

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generated nerve or from maturation of regenerated nervefibers and resorption of collateral needles branches of sin-gle completely regenerated axon [29,30].

Extracellular matrix formation and subsequent tissue re-generation depend on diameter and length of implanted tubeand nerve tissue defect [27].

Membranes and fibers with potential application forperipheral nerve regeneration

Polymers membranesBoth biostable as well as biodegradable polymers are

used as the carrier materials for regeneration of peripheralnerve. Most popular stable polymer materials are epoxyresins, polytetrafluoroethylene, polyimide and first of all sili-con rubber. These polymers are biocompatible, electricallyinsolating and stable. To improve biocompatibility of poly-mer- based implants their bulk and surface properties canbe modified in wide range[18].

Classic example of artificial implant used in surgery formany years are silicone tubes. Investigations of this mate-rial provided several important informations about nerve re-generation process [31,32]. Silicone tubes provide an "ex-trinsic" closed space within of which a spontaneously formedfibrin matrix allows for ingrowth of axons and non-neuronalcells [33]. One of silicone implants drawback is mismatch-ing mechanical properties to those of tissue. Moreover, sili-cone material strongly stimulates fibrous tissue formation,and by consuming tube space limits or even inhibits regen-eration, migration of axons from proximal to distal stump[34].

Actually biodegradable materials are being examined, inorder to eliminate necessity of second operation for nerveguide removal after nerve regeneration is completed [35].

Several biodegradable synthetic materials, in the formof simple hollow conduits, have been shown to support nerveregeneration. Biodegradable polymers used as membranesor channel to regeneration of peripheral nerve are poly-l-lactide acid (PLLA), poly-glycolic acid, copolymer poly-l-lactide-co-glycolic acid (PGLA), chitosan, collagen and poly-3-hydroxybutyrate (PHB).

Polyesters, such as polylactic acid (PLA), polyglycolicacid (PGA), poly-lactide-e-caprolactone and PLGA havebeen used extensively due to their availability, processabilityand low inflammatory response [36]. A suitable materialshould be biocompatible, probably bioresorbable, benefi-cial to nerve regeneration and maturation, resistant to scarinvasion, and clinically applicable. PLLA, and polyglycolidacid (PGA) offer several advantages including their biode-

mórki Schwanna w trakcie postêpowania regeneracji akso-nu s¹ stwierdzane przed lub za sto¿kiem wzrostowym, przyczym wiadomo, ¿e komórki Schwanna maj¹ zdolnoæ kolo-nizowaæ powstaj¹cy regenerat niezale¿nie od kontaktu zaksonami [20,22,23]. Proces regeneracji tkanki nerwu ule-ga wyranemu przyspieszeniu od 9 doby po zabiegu [21].Po zetkniêciu siê czo³a obu tych procesów (przy implancied³ugoci 10 mm nastêpuje to oko³o 16-17 dnia, przy d³ugo-ci 25 mm oko³o 21 dnia) dochodzi do ich palczastego na-chodzenia siê i przejciowego zaburzenia osiowej orienta-cji w miejscu przejcia [15,21]. Po oko³o 7 dniach aksonyprzechodz¹ do dystalnej czêci regeneratu i wykorzystuj¹cpodporê komórek Schwanna pochodz¹cych z kikuta dystal-nego, osi¹gaj¹c oko³o 21-28 dnia kikut dystalny [20,21,24].Ich wzrost nastêpuje teraz wed³ug kierunku okrelonegoprzez uk³ad tych komórek (przypomina to wrastanie w ka-na³y Büngera). Powoduje to zatrzymania namna¿ania siêkomórek Schwanna pochodz¹cych z kikuta dystalnego.Je¿eli nie dochodzi do po³¹czenia siê obu procesów ko-mórki Schwanna w kikucie obwodowym, aksony w kikucieproksymalnym, po przejciu pewnego odcinka (oko³o 4-5mm) przestaj¹ migrowaæ. Komórki Schwanna tworz¹ struk-turê na kszta³t "czapeczki", która pokrywa kikut dystal-ny[10,15,21,25,26]. Pocz¹tek mielinizacji postêpuj¹cy odkikuta proksymalnego w kierunku dystalnym obserwuje siêmiêdzy 14-36 dniem [20,22]. Jednoczenie dojrzewa sub-stancja pozakomórkowa budowana przez fibroblasty daj¹cmechaniczn¹ podporê powstaj¹cej tkance. Nadmierne po-wstawanie tkanki ³¹cznej, a nawet bliznowacenie ma miej-sce w okolicach pokrywaj¹cych powierzchnie cia³a obce-go, np. jakim jest sylikon lub w³ókna u¿ytych szwów nie-wcha³anialnych. Tkanka ³¹czna w istotny sposób zaburzaw tych rejonach orientacjê w³ókien fibryny oraz utrudniamigracjê komórek i aksonów [21]. W póniejszych fazachregeneracji w kikucie dystalnym stwierdza siê zdecydowa-nie wiêksz¹ iloæ aksonów ni¿ jest obecna w kikucie prok-symalnym. Jest to zwi¹zane z wytwarzaniem przez sto¿kiwzrostowe kilku niezale¿nie wzrastaj¹cych w³ókien, któreregeneruj¹ poprzez kikut dystalny. Zwiêksza to szanse po-wodzenia regeneracji pojedynczego aksonu [21,22]. W okre-sie drugiego tygodnia zaczynaj¹ w implant wzrastaæ naczy-nia krwionone, pocz¹tkowo od proksymalnego kikuta, na-stêpnie od dystalnego. Postêpuj¹ one za czo³ow¹ stref¹migracji komórek aksonów. Pod koniec trzeciego tygodnianaczynia spotykaj¹ siê w rodkowej strefie regeneratu una-czyniaj¹c 10 mm odcinek tkanki [20,21]. Odciêcie ukrwie-nia pochodz¹cego od kikutów nerwów praktycznie uniemo¿-liwia regeneracjê [23,27].

Zregenerowane w³ókna nerwowe s¹ cieñsze, zarównoaksony jak i os³onki mielinowe [10,15,20,21,22,25,26,28] Zczasem dochodzi do zmniejszania siê iloci aksonów orazpogrubiania siê os³onek mielinowych [22,29,30]. Pewn¹specyfik¹ implantów sylikonowych jest tendencja do powsta-wania w³óknienia przyciennego. Prowadzi to do zaciniê-cia nerwu i wzbudzenia procesów degeneracyjnych w po-wsta³ej tkance nerwu. Niszcz¹ one w³ókna nerwowe daj¹cobraz morfologiczny tkanki porównywalny z wielokrotnymurazem zmia¿d¿eniowym [22]. Znacz¹co ró¿ni¹ siê on odprocesów starzenia siê zregenerowanego nerwu czy doj-rzewania powsta³ych w³ókien nerwowych i resorpcji niepo-trzebnych bocznych ga³êzi pojedynczego aksonu [29,30].

Formowanie macierzy pozakomórkowej, a nastêpnietkanki regeneratu jest zale¿ne od rednicy i d³ugoci zasto-sowanej rurki i ubytku [27].

RYS. 1. Rurka silikonowa.FIG. 1. Silicone tube.

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gradability, porous structure for vascularization and consist-ency in design requirements [1,37].

Polyglycolic acid is easy available, biocompatible mate-rial with good mechanical properties. It biodegrades with-out any toxic products. Implant in the form of tube made ofpolyglycolid tube filled with collagen sponge was used suc-cessfully for bridging 15 mm peroneal nerve gap in dog[38]. Similar implant, polyglycolid acid tube coated with col-lagen and filled with laminin coated collagen fibers, wasused for bridging 80 mm gap in dog's peroneal nerve. Suchimplant contains most of known factors stimulating nervetissue regeneration (tube wall protection, extracellular ma-trix support, Schwann cell base membrane signal sequences- laminin). This implant application allowed for dog's mus-cle strength restoration adequate for normal walk withoutweight support on that limb. During 12 months of observa-tion number of axons counted in regenerated tissue de-creased (degeneration of lateral processes of axon's thatsuccessfully ended regeneration creating synaptic connec-tion), an increase of myelin sheaths diameter, increase ofamplitude and decrease of signal latency in regeneratedtissue [39].

PGA implants were used in researches on humans. 43digital nerves were connected. Final effect measured in twopoint discrimination test was as follows: 43% results werevery good (S4 score British Medical Research Council) and43% good (S3+ score BMRC). Treatment outcome was sta-tistically better comparing to classic methods. Differencewas greater for short gaps (4 mm and less) than for long (8-30 mm) [40]. In another study good results were indicatedalso for long gaps with 3 cm length [24].

The most promising material for reconstruction of pe-ripheral nerve was poly-3-hydroxybutyrate (PHB). PHB is anatural biological polymer, manufactured as bioresorbablesheets, which can be formed into tubes [41]. PHB is anenergy storage product of bacterias, occurring within thecell cytoplasm as granules. It is available in the form ofbioabsorbable sheets, which are non-antigenic, easy tohandle and have good tensile strength. PHB undergoes hy-drolytic degradation and is completely absorbed within 24-30 months [42].

Chitosan is one of the most popular polysaccharidesfound in nature [43]. Natural polysaccharide usually con-tributes to cellular adhesion and inhibition of scar forma-tion. Chitosan membranes and fibers have excellentneurogial cell affinity. Such material may repair certain dis-tant nerve injury, causing little or no immune reaction of thebody [44]. Chitosan is very hydrophilic allowing for its ex-pansion in contact with water. However, its porous formsare attempted to be used as the constructs at artificial ex-tracellular matrix suitable for the growth of neural cells. Themolecular structure of chitosan is similar to that ofglycosaminoglican, which resides in the basal membraneand extracellular matrix. It make it reacts with extracellularadhesive molecular, such as laminin, fibronectin and colla-gen IV, which promote cells to adhere, migrate and differ-entiate [44,45].

Collagen belongs to the most often used materials fornerve guide preparation due to its biocompatibility and de-sirable tensile strength [46]. Collagen is the main protein ofconnective tissue in animals and the most abundant pro-tein in mammals, making up about 1/4 of the total proteins.Over 3 year observation, with proved usefulness of colla-gen implants for peripheral nerve gaps bridging [47,48].Studies of regeneration processes in silicone and collagentubes revealed their similarity. Important factor is stimula-tion of regeneration in prefilled tubes. Tubes are filled withcollagen type I, mixture of type I and IV or collagen bondedwith chondroityn sulphate [26]. Collagen implant durability

Membrany i w³ókna mog¹ce znaleæ zastosowanie jakoimplanty do uzupe³niania ubytków w nerwach obwo-dowych.

Membrany polimerowePolimery, zarówno stabilne jak i biodegradowalne, s¹

najbardziej obiecuj¹cymi materia³ami do produkcji implan-tów dla regeneracji nerwów obwodowych. Najbardziej po-pularnymi polimerami niebiodegradowalnymi s¹ ¿ywiceepoksydowe, politetrafluoroetylen, poliimidy, a przedewszystkim silikon. Wymienione polimery s¹ biozgodne, trwa-³e, a pod wzglêdem elektrycznym s¹ izolatorami. Wiêkszoæw³aciwoci polimerów mo¿e byæ w pewnym stopniu mo-dyfikowana, tak¿e powierzchnia polimerów mo¿e ulegaæmodyfikacji w celu poprawienia jej biozgodnoci [18].

Klasycznym obecnie przyk³adem sztucznego implantus¹ rurki sylikonowe stosowane od wielu lat w chirurgii. Ba-dania z ich u¿yciem dostarczy³y wielu danych o procesachregeneracji zachodz¹cych w nerwach obwodowych [31,32].Rurki silikonowe stanowi¹ zamkniête rodowisko, wewn¹trzktórego nastêpuje samoistne formowanie siê macierzy fi-bryny. Pozwala ona na wzrost aksonów, naczyñ w³osowa-tych i migracjê komórek podporowych [33]. Wad¹ implan-tów silikonowych jest niedopasowanie ich w³asnoci me-chanicznych z w³asnociami mechanicznymi tkanek, z któ-rymi implant jest po³¹czony, a tak¿e fakt, ¿e jest to materia³niebiodegradowalny. Ponadto materia³ sylikonowy silniestymuluje powstawanie tkanki w³óknistej, która przerasta-j¹c wiat³o rurki ogranicza b¹d wrêcz uniemo¿liwia rege-neracjê, przerastanie w³ókien nerwowych z czêci proksy-malnej do czêci dystalnej ubytku [34].

Obecnie d¹¿y siê do zastosowania degradowalnychmateria³ów, aby unikn¹æ potrzeby ponownej operacji w celuusuniêcia "nerve guide", gdy ca³kowita regeneracja nerwudobiegnie koñca [35].

Wiele biodegradowalnych materia³ów syntetycznych wformie prostych, wdr¹¿onych wewn¹trz kana³ów jest wyko-rzystywanych jako podpory dla regeneracji nerwów. Poli-mery bioresorbowalne stosowane do regeneracji nerwówwystêpuj¹ce w formie membran b¹d kana³ów to: polilak-tyd (PLA), poliglikolid, kopolimer poli-l-laktydu z poliglikoli-dem (PGLA), chitozan, kolagen, poli-3-hydroksybutyren(PHB).

Poliestry takie jak polilaktyd (PLA), poliglikolid (PGA), poli-e-kaprolakton i kopolimer laktydu z glikolidem (PLGA) s¹stosowane w szerokim zakresie poniewa¿ s¹ ³atwo dostêp-ne, proste w obróbce i wywo³uj¹ niewielki odczyn zapalny[36]. Odpowiedni materia³ powinien byæ biozgodny, ulegaæbioresorpcji, podtrzymywaæ regeneracjê nerwów i ich kszta³-towanie, a dodatkowo byæ porêczny chirurgicznie. Polilak-tyd (PLA), poliglikolid (PGA) wykazuj¹ sporo pozytywnychcech takich jak: biodegradowalnoæ, biozgodnoæ oraz po-rowat¹ strukturê odpowiedni¹ dla tworzenia siê naczyñkrwiononych [1,37]

Kwas glikolowy jest ³atwo dostêpnym, biozgodnym ma-teria³em o dobrych w³aciwociach mechanicznych. Ulegabiodegradacji nie wytwarzaj¹c toksycznych produktów. Im-plant zbudowany z rurki poliglikolidowej wype³nionej kola-genem zosta³ zastosowany z powodzeniem dla uzupe³nie-nia 15 mm ubytku nerwu strza³kowego u psa [38]. Podobnyimplant sk³adaj¹cy siê z rurki poliglikolidowej pokrytej kola-genem i wype³nionej w³óknami kolagenowymi pokrytymilaminin¹ zastosowano dla uzupe³nienia ubytku 80 mm ner-wu strza³kowego równie¿ u psa.

Implant mtaki zawiera wiêkszoæ znanych czynnikówwspomagaj¹cych regeneracjê nerwu (os³onê rurki, podpo-rê macierzy komórkowej, sekwencje sygna³owe b³ony pod-stawnej dla komórek Schwanna - laminina). Zastosowanietakiego implantu pozwoli³o uzyskaæ powrót si³y miêniowej

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is modified using UV, heat treatment or glutar aldehyd. Heattreated collagen is fully absorbed after 6 weeks, well vas-cularised, nerve tissue is divided in pseudofascicles withlarge quantity of dense cicatricle tissue. UV treated mate-rial is poorly vascularised, nerve tissue maturates and after12 weeks is comparable to autograft (number of myelinedaxons, muscle evoked potentials) [49]. Glutaraldehyd cre-ates strongly hydrophobic and cytotoxic surface that greatlyinhibits regeneration process [49,50]. Except of physicalfeatures of implant such, as pore network, pore diameter,three-dimensional canals localization, implant preparationtechnique is also important, and may greatly change its re-generative properties [49].

Previous studies have shown that collagen tubes cannotbe used to bridge nerve defects greater than 15mm, sincea long collagen tube can break and its lumen could col-lapse due to movement. Sometimes a collagen tube with alength of 20mm and an inner diameter of 1mm was coatedwith polymer, for examples poly(l-lactide-co-glycolic acid)(PLGA) to enhance its structural integrity and elasticity. Thepolymer layer performs two roles: reinforces collagen mem-brane and prevents collapse due to movement. On the other,hand, it creates a highly porous structure, which is impor-tant determinants for nutrient transport into the conduit .The collagen layer also prevents surrounding tissue frominvading the tubes [51,52,53].

The polymers conduits are very often filled with fibersmaterials like poly(l-lactide-co-glycolide) (PLGA) fibers, poly-l-lactide acid (PLLA), alginian filaments and hydrogels, col-lagen filaments, carbon filaments, bioglass fibers, chitosanfibers or material with properties of hydrogel [44,54].

Collagen fibers can be used as scaffolds for axonal elon-gation. Collagen is a major component of the extracellularmatrix and is known to promote cellular proliferation andtissue healing. It has also been reported that the biologicalproperties of collagen make it a superior choice for the usein conjunction with nerve tubes as a promoter of peripheralnerve regeneration [37,55]. Nerve scaffold made of the col-lagen filaments can be length from 20 to 30mm and 20µmin diameter [56].

Bioglass fibers are not only biocompatible andbioresorbable, what are the fundamental requirements ofsuccessful devices, but also amenable to bioengineering.Such fibers have the potential for the use in the most chal-lenging clinical cases, where there are long inter-stump gapsto be bridged. Bioglass fibers can be used to deliver growthfactors and/or adherent cells within the lumen of a nerveconduit. Bioglass fibers used as scaffolds for axonal regen-eration consist of SiO3, Na2O, CaO and P2O5 and, their di-mensions are 0,5cm long and 25µm diameter. Scientistsfrom United Kingdom have applied bioresorbable bioglassfibers as a scaffolds for axonal regeneration. 0,5cm frag-ment at the sciatic nervesof adult rats was reconstructed.The axonal regrowth was qualitatively and quantitively in-distinguishable from that seen using an autograft [57].

Alginian based hydrogels are well recognized materialsboth in experimental studies as well as in clinical applica-tions [58]. It is natural polymer extracted from sea algae,composed by turn of mannose and glucuronic acid. Ca ionsaddition to water alginate solution cause ionic bonds crea-tion between polymer chains. This process turns the solu-tion into hydrogel, and its solidity can be controlled by con-centration of Ca ions [59]. Lack of specific cell bonding sec-tions makes alginate chains ideal ground for constructionof extracellular matrices. In order to facilitate material cellcolonization, alginate chains are modified with cell's bind-ing signal sequences. The most common sequence is RGD[59,60,61]. Alginates can be easing sterilized or modifiedchemically in order to change their properties [59]. 10 mm

u psa umo¿liwiaj¹cy zwierzêciu normalny chód. W czasie12 miesiêcznej obserwacji stwierdzono zmniejszenie siê licz-by aksonów w regeneracie (degeneracja bocznych wypu-stek aksonów, które wytworzy³y po³¹czenia) powiêkszaniesiê rednicy os³onek mielinowych, spadek latencji przewo-dzenia sygna³ów przez zregenerowany nerw [39].

Implanty na bazie PGA zosta³y zastosowane w bada-niach na ludziach. W jednym z badañ wykonano zespole-nie 46 nerwów palcowych uzyskuj¹c w badaniu czucia dwu-punktowego po 43 % wyników bardzo dobrych (S4 wed³ugBritisch Medical Research Council) i dobrych (S3+ wed³ugBMRC). Wynik leczenia by³ statystycznie lepszy w porów-naniu do metod klasycznych. Ró¿nica by³a bardziej widocz-na dla bardzo krótkich ubytków (do 4 mm) ni¿ d³u¿szych (8-30mm) [40]. Kolejne badania wykaza³y dobre wyniki lecze-nia dla ubytków o d³ugoci 3 cm [24].

Bardzo obiecuj¹cym materia³em dla regeneracji nerwówobwodowych jest poli-3-hydroksybutyren (PHB). PHB jestnaturalnym polimerem, produkowanym jako bioresorbowal-ne warstwy, które mog¹ byæ nastêpnie przetwarzane w po-staæ rurek [41]. PHB w postaci granul wystêpuje w sposóbnaturalny w cytoplazmie komórki bakterii jako substancjamagazynuj¹ca energiê. PHB jest dostêpny jako bioresor-bowalne warstwy, o niskiej antygenowoci, jest porêczny icechuje siê dobr¹ wytrzyma³oci¹ na rozci¹ganie, PHB ule-ga degradacji hydrolitycznej i jest ca³kowicie usuwany wci¹gu 24-30 miesiêcy [42].

Chitozan jest jednym z najczêciej wystêpuj¹cych wnaturze polisacharydów o ³adunku dodatnim (chitozan jestw ca³oci b¹d czêciowo otrzymywany przez deacetylacjêchityny) [43]. Naturalne polimery wykazuj¹ wysokie zdol-noci adhezji komórek oraz inhibicji powstawania blizny.Membrany oraz w³ókna chitozanowe wykazuj¹ doskona³epowinowactwo do komórek neurogleju, dziêki czemu ma-teria³ ten mo¿e byæ z powodzeniem wykorzystany do re-konstrukcji uszkodzonych nerwów. W niewielkim stopniu lubnawet wcale wywo³uje reakcje immunologiczn¹ organizmu[44]. Chitozan jest bardzo hydrofilny, co powoduje, ¿e wch³a-nia du¿e iloci wody, jest wysoko porowatym materia³em,przez co mo¿e byæ wykorzystany do konstrukcji sztucznejmacierzy zewn¹trzkomórkowej odpowiedniej dla wzrostukomórek nerwowych. Struktura molekularna chitozanu jestpodobna do glikozaminoglikanów, które znajduj¹ siê w b³o-nie podstawowej oraz w macierzy zewn¹trzkomórkowej.Sprawia to, ¿e chitozan w ³atwy sposób oddzia³uje z ze-wn¹trzkomórkowymi cz¹stkami adhezyjnymi takimi jak la-minina, fibronektyna oraz kolagen typu IV, które pobudzaj¹komórki do adhezji, migracji oraz ró¿nicowania siê [44,45].

Kolagen jest jednym z najczêciej stosowanych mate-ria³ów do produkcji "nerve guide" z powodu jego biozgod-noci oraz po¿¹danej wytrzyma³oci na rozci¹ganie [46].Kolagen jest g³ównym bia³kiem tkanki ³¹cznej zwierz¹t oraznajczêstszym bia³kiem wystêpuj¹cym u ssaków, stanowi¹-cym oko³o 1 wszystkich bia³ek. Ponad 3 letnia obserwacjana naczelnych potwierdzi³a przydatnoæ kolagenowych po-mostów do uzupe³niania ubytków nerwów obwodowych[47,48]. Kolejne badania wskazuj¹ na identycznoæ proce-sów regeneracyjnych na bazie kolagenu i rurek sylikono-wych. Wa¿nym aspektem jest stymulacja regeneracji w przy-padku wype³nienia rurek. Stosuje siê macierze zarówno zczystego kolagenu typu pierwszego, jak i mieszanin typu I iIV oraz kolagenu po³¹czonego z siarczanem chondroityny[26]. Dla podniesienia wytrzyma³oci implantu kolagenowe-go stosuje siê obróbkê przy u¿yciu ultrafioletu, ogrzewanialub poddanie wp³ywowi aldehydu glutarowego. Kolagenpoddany obróbce termicznej ulega wch³oniêciu po 6 tygo-dniach, jest dobrze unaczyniony, powstaj¹ca na jego bazietkanka nerwowa jest podzielona w pseudopêczki z du¿¹iloci¹ gêstej tkanki bliznowatej. Materia³ poddany obróbce

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alginate sponge implanted as a bridge for nerve regenera-tion is absorber in 4 weeks. During that time axons manageto pass the gap. Characteristic is fact, that ingrowth of tis-sue into the implant starts with axons followed by Schwanncells. Schwann cells produce fully valuable myelin sheath.Simultaneously with proximal regeneration into the implantSchwann cells migrate from distal stump and create tube-routs for approaching axonal growth cones. After connec-tion of these processes axons start to ingrowth into distalpart of regeneration and elongate using Schwann cell tubes.This process proceeds off-centre, firsts taking place in pari-etal, and secondly in central part of implant. This aspect ofregeneration is dependent on gel degradation preceded fromexternal part of implant, gradually creating looser, easer pen-etrable environment for regenerating tissue. It points to factthat, at lest for alginate, more important factor controllingimplant colonization are degradation processes than that ofpore diameter. Morphological analysis of the regeneratedtissue revealed of regenerated axon. The amount of suchaxons the presence corresponded to the half of the numberat uninjured part of nerve, and electrophysiological analy-sis proved existence at functional connections [30]. Axonalelongation and creation of functional connections with tar-get organ is possible for unmodified 50 mm alginate im-plants [62].

Neurotrofic substances in artificial nerve implantsFor improvement of neuroregeneration promoting prop-

erties polymers tubes prior implantation are filled with sev-eral neurotrophic factors, which can promote early periph-eral nerve regeneration. The most commonly used neurite-promoting factors include collagen gel, laminin andfibronectin [63,64] and the most extensively studied neuro-trophic factor, nerve growth factor (NGF) [65]. The effect ofNGF grafted onto membranes indicates that the procedureused in immobilization of NGF onto polymers membranemay be beneficial for adhesion of Schwann cells on themembranes. The immobilization NGF on polymer mem-brane is following: polymer membranes were soaked inchemical solution, for examples in 1-ethyl-3-(3dimethylaminopropyl) carbodiimide (EDAC) solution andthen transferred to NGF solution. In this process NGF re-acts with bonds existed on the surface of polymer mem-branes [66].

Extracellular matrix fibers like laminin, fibronectin and col-lagen play important role in every tissue regeneration proc-ess [32]. Laminin is mainly produced by Schwann cells andwidely dispersed in the peripheral nervous system.Fibronectin can be found in plasma, fibrous tissue, and base-ment membrane. Fibroblasts and Schwann cells also pro-duce significant amounts of fibronectin. Laminin, fibronectinand collagen are major constituent of all extracellular matri-ces. Prefilling of nerve tube implants with these fibers cangreatly enhance nerve regeneration processes in implant.

In order to improve peripheral nerve regeneration poly-mers conduits are incorporating with allogenic Schwann cells(SCs). The SCs are harvested, cultured to obtain confluentmonolayers and injected into the biopolymers conduits [1].Schwann cells play a crucial role in regeneration of periph-eral nerves due to their neurotrophic influence, mechanicsupport and providing protection with myelin sheet. Schwanncells produce and accumulate trophic factors for regenerat-ing axons and thus are essential for axonal regeneration,particularly for long gaps [44,67,68]. Schwann cells producebasal lamina components, such as collagen IV, which pro-vide the extracellular matrix for attachment of the regener-ating axons [1,69,70,71]. Precolonization of the implant withthese cells shortens the time of regeneration by eliminationof the fibrin bridge and it's cellular colonization period. Allo,

UV jest s³abo unaczyniony, jednak wstaj¹ca weñ tkankanerwowa szybko dojrzewa osi¹gaj¹c po 12 tygodniach po-staæ podobn¹ do autoprzeszczepu [49]. Glutaraldehyd po-woduje powstanie powierzchni o silnej hydrofobowoci orazcytotoksycznoci, co znacznie upoledza procesy regene-racyjne wewn¹trz takiego implantu [49, 50]. Oprócz w³aci-woci fizycznych implantu takich jak sieæ porów, ich redni-ca, u³o¿enia przestrzenne kana³ów wa¿na jest technika przy-gotowania implantu, która mo¿e znacznie wp³yn¹æ na jegow³aciwoci [49].

Wczeniejsze badania wykaza³y, ¿e rurki kolagenowenie mog¹ byæ zastosowane do uzupe³niania ubytku nerwuwiêkszego ni¿ 15 mm, poniewa¿ mog¹ ulegaæ z³amaniu,b¹d zapadaniu w wyniku przemieszczeñ. W celu popra-wienia elastycznoci i odpornoci struktury na zniszczenie,rurki kolagenowe s¹ pokrywane polimerem takim jak kopo-limer polilaktydu |z poliglikolidem. Pow³oka polimerowa spe³-nia dwie funkcje: po pierwsze wzmacnia jej cianê orazzapobiega jej zapadaniu w trakcie ruchu, po drugie tworzywysokoporowat¹ strukturê, która jest bardzo wa¿na dlatransportu substancji od¿ywczych do wnêtrza implantu.Pow³oki polimerowe na powierzchni rurek kolagenowychzabezpieczaj¹ tak¿e przed wtargniêcie tkanki zewnêtrznejdo wnêtrza rurki [51,52,53]. Z³¹cza polimerowe bardzo czê-sto s¹ wype³niane materia³ami w³óknistymi takimi jak w³ók-na z kopolimeru poli-ld-laktydu z poliglikolidem (dl-PLGA),w³ókna z poli-l-laktydu (PLLA), w³ókna alginianowe, kola-genowe, wêglowe, w³ókna z bioszkie³, w³ókna chitozanowea tak¿e materia³em wype³niaj¹cym mo¿e byæ hydro¿el [44,54].

W³ókna kolagenowe mog¹ byæ u¿ywane jako pod³o¿adla wzrastaj¹cych w³ókien nerwowych. Dziêki odpowiednimw³asnociom biologicznym, w³ókna kolagenowe s¹ u¿ywa-ne jako elementy wype³niaj¹ce polimerowe implanty ner-wów, u³atwiaj¹ce ich regeneracje [37,55]. Pod³o¿a dla re-generacji nerwów wykonane z w³ókien kolagenowych mog¹mieæ d³ugoæ od 20 do 30mm i rednicê 20 µm [56].

W³ókna z bioszkie³ s¹ biozgodne i bioresorbowalne, atak¿e maj¹ mo¿liwoæ potencjalnego zastosowanie w wie-lu stanowi¹cych wyzwanie dziedzinach, na przyk³ad domostowania d³ugich przerw miêdzy kikutami. Mog¹ byæzastosowane jako elementy do transportowania czynnikówwzrostu oraz/lub jako podpora dla wzrostu komórek nerwo-wych. W³ókna z bioszkie³ stosowane jako pod³o¿a dla rege-neracji aksonów zawieraj¹ SiO3, Na2O, CaO i P2O5, przywymiarach 0,5cm d³ugoci oraz 25µm rednicy. Naukowcyz Wielkiej Brytanii zastosowali w³ókna z bioszkie³ jako pod-³o¿e dla regeneracji aksonów dla 0,5cm ubytku nerwu kul-szowego doros³ego szczura - ró¿nica pomiêdzy parame-trami odbudowanego aksonu, po zastosowaniu w³ókien zbioszkie³, a autoprzeszczepu by³a praktycznie niedostrze-galna [57].

Hydro¿ele skonstruowane na bazie alginianów s¹ do-brze poznanymi materia³ami stosowanymi zarówno w ba-daniach dowiadczalnych jak i maj¹cymi uznane zastoso-wanie w medycynie[58]. Jest to naturalny polimer izolowa-ny z alg morskich, zbudowany z po³o¿onych na przemianjednostek kwasu manuronowego i guluronowego. Dodatekjonów Ca do roztworu wodnego alginianów powoduje po-wstawanie wi¹zañ jonowych pomiêdzy ³añcuchami polime-ru, co prowadzi do przechodzenia roztworu w postaæ hy-dro¿elu. Stopieñ upostaciowienia mo¿e byæ regulowany stê-¿eniem dodanych jonów Ca [59]. Ze wzglêdu na brak spe-cyficznych miejsc ³¹czenia z komórkami w ³añcuchach po-limeru alginiany s¹ idealnym pod³o¿em do konstrukcjisztucznych macierzy pozakomórkowych [59,60,61]. Alginia-ny poddaj¹ siê prostym procesom sterylizacji, s¹ ³atwe wmodyfikacji chemicznej celem zmiany w³aciwoci [59].Zastosowano g¹bki alginianowe jako pomosty dla regene-

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kseno i autogenic cells are used, pre or not predegenerated.The best effects are found with autogenic, preinduced cells[72,73].

Microelectrodes for nerve regeneration

Interesting investigation areas pertain to composite im-plants used for stimulating nerve regeneration, passive ex-tracellular matrix support and active electrical stimulation ofnerve regeneration. These systems consist ofmicroelectrodes placed on a sieve-shaped plate containinglong, narrow holes, round in shape. The microelectrodesare situated close to the holes or constitute a part of thehole wall [74]. The electrode array of via holes is adaptedinto the expected path of the regenerating fibers in a fash-ion that the nerve fibers are allowed to regenerate throughthe perforations of the device. In order to assure the me-chanical stability of all system, the electrodes are placedbetween polymer channel connecting proximal nerve stumpwith distal one.

The advantage of this approach is that the electrodesare in near contact with the nerve fibers, thas allowing forboth accurate recording and efficient stimulation. The dis-advantage of this method is that the nerve has to be cut inorder to regenerate through the implanted device. The suc-cess of the whole operation can be assessed only severalweeks after implantation, when the axons have been re-generated through the device. Sometimes, there is a possi-bility that nerve fibers may be damaged by the mechanicalload imposed by the electrode or by the force within the viaholes, especially over long term implantation [74,75].

Various techniques and materials have been used to fab-ricate the needed sieve electrodes. Some early electrodeswere realized by embedding 25mm-diameter hollow goldcylinders into porous Teflon. Other was realized by mechani-cally drilling 100mm-diameter holes into epoxy modules andthen embedding 77mm-diameter Teflon-coated silver wiresinto the holes [76]. The material very often used in the con-struction of regenerative electrodes is silicon. The siliconelectrodes with dimensions and number of via holes com-patible with the characteristics of peripheral nerves wereused in axonal regeneration nerves of rat, and frog [19,21].However, such silicon interfaces cause frequent signs ofaxonopathy, and constitute a physical barrier that limits theelongation of regenerating axons depending on the size ofthe via holes [75,76]. Recently the silicon electrodes arereplaced by polyimide-based electrodes. Polyimide allowsto make a higher number of holes than silicon dice of thesame total area and to be micromachined in a variety ofdesigns suitable for implantation in different nerve models.

racji ubytku nerwu o d³ugoci 10mm i zaobserwowano ichca³kowite wch³oniêcie w ci¹gu 4 tygodni przy jednoczesnejregeneracji aksonów. Charakterystyczny jest fakt, ¿e wra-stanie tkanki w implant zaczyna siê od aksonów, za którymipod¹¿aj¹ komórki Schwanna. Wytwarzaj¹ one w pe³ni war-tociowe os³onki mielinowe. Jednoczenie od bieguna dy-stalnego w obrêb implantu nape³zaj¹ komórki Schwannatworz¹c tory dla zbli¿aj¹cych siê sto¿ków regeneruj¹cychaksonów w³ókien nerwowych. Po zetkniêciu siê tych dwóchprocesów dochodzi do przejcia aksonów z proksymalne-go pola wzrostowego w dystalne i dalszy wzrost na bazieutworzonego przez komórki Schwanna pod³o¿a. Procesyte zachodz¹ ekscentrycznie zajmuj¹c najpierw obrze¿eimplantu a nastêpnie coraz bardziej centralne czêci. Jestto zwi¹zane z procesami degradacji ¿elu, który postêpowa³stopniowo od zewn¹trz do wewn¹trz, tworz¹c rodowisko³atwiej penetrowane przez regeneruj¹c¹ tkankê. Wskazujeto, ¿e przynajmniej w przypadku alginianów, wa¿niejszymczynnikiem kontroluj¹cych kolonizacjê implantu przez tkan-kê s¹ procesy jej degradacji ni¿ wielkoæ porów. Badaniamorfologiczne wykazuj¹ obecnoæ zregenerowanych akso-nów w iloci odpowiadaj¹cych po³owie iloci obecnych postronie zdrowej, a badania elektrofizjologiczne wykazuj¹wytworzenie funkcjonalnych po³¹czeñ [30]. Wed³ug badañmo¿liwe jest uzyskanie przechodzenia aksonów przez nie-wzbogacone implanty alginianowe o d³ugoci 50mm z wy-tworzeniem funkcjonalnych po³¹czeñ [62].

Mo¿liwoci wykorzystania substancji neurotroficznych wsztucznych implantach nerwowych

Dla zwiêkszenia w³aciwoci neuroregeneracyjnych rur-ki polimerowe stosowane jest wzbogacanie ich przed im-plantacj¹ ró¿norodnymi czynnikami neurotroficznymi, dlapobudzenia wczesnych faz regeneracji nerwów obwodo-wych. Najczêciej stosowanymi czynnikami neurotroficzny-mi s¹ ¿el kolagenowy, laminina, fibronektyna [63,64], oraznajlepiej poznany czynnik stymuluj¹cy neuroregeneracjê -czynnik wzrostu nerwu (NGF - nerve growth factor) [65].Immobilizacja czynnika NGF we wnêtrzu membrany poli-merowej mo¿e wspomagaæ adhezjê komórek Schwanna.Proces immobilizacji NGF do wnêtrza membrany odbywasiê nastêpuj¹co: membrana polimerowa najpierw zanurzo-na zostaje w roztworze chemicznym np. 1-ethyl-3-(3 dime-thylaminopropyl) carbodiimide (EDAC), a nastêpnie prze-niesiona do roztworu NGF. W wyniku tego procesu NGFreaguje z wi¹zaniami znajduj¹cymi siê na powierzchni mem-brany polimerowej [66].

W procesie regeneracji wszystkich tkanek istotny udzia³maj¹ w³ókna macierzy pozakomórkowej: laminina, fibronekty-na oraz kolagen [32]. Laminina jest g³ównie produkowana przezkomórki Schwanna, wystêpuje w du¿ej iloci w ca³ym obwo-dowym uk³adzie nerwowym. Fibronektyna jest obecna w pla-zmie, tkance w³óknistej oraz b³onie podstawnej. W znacznejiloci produkowana jest przez fibroblasty oraz komórki Schwan-na. Wype³nienie tymi materia³ami implantowanych tub pozwalana znaczn¹ modyfikacjê i przyspieszenie procesów regenera-cji zachodz¹cych w implancie.

W celu przyspieszenia regeneracji nerwów obwodowychstosuje siê wzbogacanie implantów komórkami Schwanna(SCs) pochodzenia allogenicznego. Komórki Schwanna s¹hodowane w celu uzyskania konfluentnej monowarsty, anastêpnie wstrzykiwane do wnêtrza implantu polimerowe-go [1]. SC pe³ni¹ decyduj¹c¹ rolê w regeneracji nerwów zuwagi ich neurotropowe i neurotroficzne w³aciwoci. Sta-nowi¹ podporê mechaniczna dla regeneruj¹cych aksonów,wytwarzaj¹ oraz akumuluj¹ czynniki od¿ywcze dla regene-ruj¹cych siê aksonów, co jest szczególnie wa¿ne przy du-¿ych ubytkach nerwu [44,67,68]. Komórki Schwanna pro-dukuj¹ tak¿e sk³adowe blaszki podstawnej, takie jak kola-

RYS. 2. Schemat elektrody dla regeneracjinerwów. [74].FIG. 2. Electrode scheme for nerves regeneration.

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Polyimide-based electrodes have been shown to bebiocompatible and stable over several months of in vivoimplantation and testing [79].

Nanomaterials for nerve regeneration

Good results of research using carbon nanostructures incentral nervous system nerve cells cultures indicatestheirpotential for the treatment peripheral nervous system. Prom-ising interactions are found between neurons and nanoscalematerials with potential minimalization of astrocytic spinalcord scar tissue formation. Carbon nanofibers are particu-larly attractive for the use in neural biomaterials not onlydue to these special properties, but also due to their highconductivity. Further investigation of carbon nanofiber ma-terials is required to verify their properties as potential neu-ral biomaterials [80,81,82].

Carbon nanotubes (CNT) are strong, flexible and con-duct electrical current. Moreover, their biocompatibility andstabi8lity in living organism have already been proved [80].They can be functionalized with different biomolecules likeneuron growth factors and adhesion agents. These proper-ties are useful in the formation of neuron hybrids. Such ca-pabilities of carbon nanotubes make them potentiallysuitablel candidates to form scaffolds to guide neurite out-growth. Zhang at al., demonstrated the capability offunctionalized patterned vertical carbon nanotube arrays assupport platforms for guiding neurite growth and formingsynoptically communicative network. The study indicatedthat neurons "in vitro" conditions created communicativesynaptic bridge between two nanotube patterns with a dis-tance of separation of 20mm [83]. Telford et al., have cul-tured nerve cells from the brain's hippocampus region onsubstrates coated with network of carbon nanotubes, andfound a large increase in neural signal transfer betweencells. The data provided information on the supportive de-vices for bridging and integrating functional neuronal net-work "in vitro". [84].The results will impact on new tissueengineering strategies, where functional reconnectionamong neurons or the improvement in neural signal trans-fer is the main target. There is strong demand for deeperstudy on the properties of such materials and their physi-ological interactions with neurons in culture. This will pro-vide the base for more exhaustive evaluation on animalmodels.

gen typu IV czy laminina, które u³atwiaj¹ kontakt regeneru-j¹cych w³ókien nerwowych z macierz¹ zewn¹trzkomórko-w¹ [1,69,70,71]. Wzbogacenie implantu tymi komórkamiskraca okres regeneracji o czas potrzebny na uformowaniepomostu fibrynowego i skolonizowanie go przez nadpe³za-j¹ce komórki Schwanna. Najkorzystniejsze wyniki daje za-stosowanie autogennych wzbudzonych komórek Schwan-na [72,73].

Mikroelektrody w regeneracji nerwów

Jednym z ciekawych podejæ badawczo-eksperymental-nych s¹ badania z u¿yciem kompozytowych implantówwykorzystuj¹cych stymuluj¹cê regeneracjê w³ókien nerwo-wych w³aciwoci biernego podparcia tkanki i czynnej sty-mulacji elektrycznej. Uk³ady te zbudowane s¹ z mikroelek-trod umieszczonych na p³ytce w kszta³cie sita zawieraj¹cejd³ugie, w¹skie, okr¹g³e otwory. Mikroelektrody usytuowanes¹ na brzegu otworów b¹d s¹ czêci¹ cianek otworów[74]. Elektrody umieszczane s¹ w taki sposób w ubytkunerwu, aby regeneruj¹ce siê w³ókna nerwowe mog³y prze-chodziæ przez znajduj¹ce siê w niej otwory.

W celu zapewnienia mechanicznej stabilnoci ca³egouk³adu, elektrody usytuowane s¹ pomiêdzy polimerowymikana³ami ³¹cz¹cymi kikut proksymalnym nerwu z kikutemdystalnym.

Zalet¹ tego typu rozwi¹zania jest fakt, ¿e urz¹dzenieznajduje siê w bliskiej odleg³oci od w³ókien nerwowych, copozwala na skuteczn¹ ich stymulacjê. Powodzenie opera-cji mo¿e zostaæ ocenione w przeci¹gu kilku tygodni po im-plantacji, kiedy w³ókno nerwowe zdo³a zregenerowaæ po-przez urz¹dzenie. Czasami w³ókna nerwowe mog¹ ulecuszkodzeniom w wyniku naprê¿eñ mechanicznych pocho-dz¹cych od elektrody b¹d przez si³y dzia³aj¹ce wewn¹trzotworów powsta³e w wyniku ich zarastania, zw³aszcza przyd³ugim okresie implantacji [74,75].

Ró¿norodne techniki oraz materia³y by³y stosowne przykonstruowaniu elektrod. Pocz¹tkowo wykonywane by³y po-przez zatopienie z³otych, pustych wewn¹trz cylindrów o red-nicy 25µm w porowatym teflonie. Innym sposobem jestmechaniczne wiercenie dziur o rednicy 100µm w elemen-cie epoksydowym, a nastêpnie umieszczenie wewn¹trz nichsrebrnych drutów pokrytych teflonem [76]. Materia³em u¿y-wanym najczêciej do konstrukcji elektrod do regeneracjinerwów jest krzem. Elektrody krzemowe o odpowiednichwymiarach i iloci otworów stosowane by³y do regeneracjiaksonów nerwów u szczura oraz ¿aby [19,21].

Jednak¿e, krzem powoduje czêsto objawy aksonopatii istanowi fizyczn¹ barierê ograniczaj¹c¹ wyd³u¿anie regene-ruj¹cych siê aksonów [75,76]. Obecnie elektrody krzemo-we zastêpowane s¹ elektrodami na bazie poliimidów. Wprzypadku poliimidów istnieje mo¿liwoæ wytworzenia wiêk-szej iloci otworów dla tej samej powierzchni ca³kowitej wporównaniu z p³ytk¹ krzemow¹, a tak¿e istnieje mo¿liwoæstworzenie odpowiedniego modelu nerwu dopasowanegodo miejsca implantacji. Elektrody na bazie poliimidu s¹ bio-kompatybilne i stabilne zarówno w warunkach "in vivo" jak ipodczas prób mechanicznych [79].

Nanomateria³y w regeneracji nerwów

Obiecuj¹ce wyniki zastosowania nanorurek wêglowychw badaniach na komórkach orodkowego uk³adu nerwo-wego pozwalaj¹ na potencjalne ich zastosowanie w rege-neracji obwodowego uk³adu nerwowego. Odkryto, bardzointeresuj¹ce oddzia³ywanie pomiêdzy neuronami, a mate-ria³ami w skali nano, w wyniku którego nastêpuje os³abie-nie tworzenia siê tkanki bliznowatej rdzenia krêgowego.

RYS. 3. Mikrofotografia przedstawiaj¹cakomunikuj¹ce siê miêdzy sob¹ sieci synaptycznena pod³o¿u z nanorurek wêglowych [83].FIG. 3. Microphotograph of carbon nanotubessupport for forming synoptically communicativenetwork [83].

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Conclusion

Present state of knowledge on regeneration processesof peripheral nervous tissue allows for achieving good re-generation results with artificial implants. Some materialstested on animal models are now verified in the treatmentof digital nerve injuries in humans. Consecutive investiga-tions are however demanded for furtherr development ofknowledge relevant to nervous tissue regeneration.

Pimiennictwo Reference

[1] G.R.D. Evans,K. Brandt , S. Katz, P. Chauvin, L. Otto, M. Bogle,B. Wang, R.K. Meszlenyi, L. Lu, A.G. Mikos,Ch.W. Patrick Jr "Bio-active poly(l-lactic acid) conduits seeded with Schwann cells forperipheral nerve regeneration" Biomaterials 23 (2002) 841-848.[2] Pielka S., Rutowski R., Bogdan K., Pytlasiñski M., Wi¹cek R."Uszkodzenia nerwów koñczyny górnej u 1739 chorych w materia-le Kliniki Chirurgii Urazowej i Chirurgii Rêki AM we Wroc³awiu" IIIMiêdzynarodowy Kongres Polskiego Towarzystwa Chirurgii RêkiBia³ystok 2003.[3] B.R. Rutowski, S. Pielka, J. Gosk, D. Szarek, W. Urbañski "Oce-na wyników operacji mikrochirurgicznych w uszkodzeniach ner-wów koñczyny górnej." Krzysztof; Adv Clin Exp Med 2005, 14, 6,1199-1209.[4] J. Braga-Silva "The Use of Silicone Tubing in the Late Repair ofThe Median and Ulnar Nerves in the Forearm" Journal of HandSurgery (British and European Volume) 24B (1999) 6 703-706[5] J. Haftek, H. Kasprzak, A. Radek, W. Jarmundowicz, J. Jó-wiak " Przeszczepy nerwowe w rekonstrukcji uszkodzonych pninerwowych" Neurologia Neurochirurgia Polska, 1983, 17, 2, 253-258.[6] Yuan Y., Zhang P., Yang Y., Wang X., Gu X. " The interaction ofSchwann cells with chitosan membranes and fibers in vitro" Bio-materials 25 (2004) 4273-4278.[7] Borschel G.H., Kia K.F., Kuzon W.M., Dennis R.G. "Mechani-cal Properties of Acellular Peripheral Nerve" Journal of SurgicalResearch 114 (2003) 133-139.[8] Haftek J. "Stretch injury of peripheral nerves." J. Bon. J. Surg;1970; 52-B, 2, 354.[9] M. Mumenthaler, H. Schliack "Uszkodzenia nerwów obwodo-wych";; PZWL 1998; str 128; 142-143[10] S. Hall "Nerve repair: a neurobilogist's view"; The Journal OfHand Surgery; vol 26b; No2; april 2001; 129-136[11] Ming-Shaung J., Chou-Ching K. L., Jia-Lin F., Rung-Jian Ch."Transverse elasticity and blood perfusion of sciatic nerves underin situ circular compression" Journal of Biomechanics 39 (2006)97-102.[12] Kwan K.M., Woo S.L-Y. "Biomechanical properties of peri-pheral nerve".[13] Sunderland S. "Nerves and nerve injures, ed.2. Edinburgh:Churchill - Livingstone, 1978.[14] T. M. Myckatyn, S.E. Mackinnon "Surgical Techniques of Ne-rve Grafting (Standard/Vascularized/Allograft)"; OperTech Orthop14:171-178; 200415] R. H. Gebelman; J.B. Lippincott "Operative nerve repair andreconstruction." Company, Philadelphia; 1991.[16] M.F. Meek "Artificial Nerve Guides - assessment of nerve func-tion", Proefschrift, 2000.[17] E.O. Johnson, A.B. Zoubos, P.N. Soucacos "Regeneration andrepair of peripheral nerves" Injury 36S (2005) 24-29.[18] Heiduscha P., Thanos S. "Implantable bioelectronic interfacesfor lost nerve functions" Progress in Neurobiology 55 (1998) 55-461.[19] G. Verrecka, I. Chunb, Y. Lib, R. Katariab, Q. Zhangb, J. Ro-senblattb, A. Decortea, K. Heymansa, J. Adriaensena, M. Bruinin-ga, M. Van Remoorterea, H. Borghysa, T. Meerta, J. Peetersa, M.E. Brewster "Preparation and physicochemical characterization ofbiodegradable nerve guides containing the nerve growth agentsabeluzole" Biomaterials 26 (2005) 1307-1315.[20] L. R. Williams, F.M. Longo, H.C. Powell, G. Lundborg, S. Va-ron,"Spatial-Temporal Progress of Peripheral Nerve RegenerationWithin a Silicone Chamber: Parameters for a Bioassay." The Jour-nal of Comparative Neurology, 218: 460-470 (1983).

Nanow³ókna wêglowe s¹ atrakcyjnym biomateria³em sto-sowanym jako implanty nerwów nie tylko z powodu szcze-gólnych w³aciwoci mechanicznych czy chemicznych, aletak¿e z powodu ich wysokiej przewodnoci w³aciwej. Dal-sze badania nad nanow³óknami wêglowymi s¹ konieczne,aby zweryfikowaæ ich potencjalne zastosowanie jako bio-materia³ów dla regeneracji nerwów [80,81,82].

Nanorurki wêglowe (CNT) s¹ materia³em trwa³ym, giêt-kim, przewodz¹cym pr¹d elektryczny, biozgodnym oraz niebiodegradowalnym [80]. Mog¹ byæ sfunkcjonalizowane ró¿-norodnymi biomoleku³ami takimi jak czynniki wzrostu neu-ronów. Takie w³asnoci nanorurek wêglowych czyni¹ z nichpotencjalnego kandydata do konstrukcji pod³o¿y dla kiero-wanego wzrostu aksonów. Zhang i wspó³. z uniwersytetu zKaliforni zademonstrowali mo¿liwoci zastosowania mode-lu (uk³adu) z pionowo u³o¿onych nanorurek wêglowych jakopodporê dla kierowanego wzrostu aksonów, a tak¿e dlatworzenia sieci po³¹czeñ synaptycznych. W badaniach "invitro" zaobserwowano, ¿e neurony tworz¹ mostki synap-tyczne pomiêdzy dwoma nanorurkowymi uk³adami (wzor-cami) oddalonymi od siebie o oko³o 20µm [83].

Telford i wspó³pracownicy opisuj¹ szereg dowiadczeñz zastosowaniem komórek nerwowych pobranych z mózguna specjalnym pod³o¿u pokrytym cie¿kami z nanorurek wê-glowych. Stwierdzono znaczny przyrost wartoci impulsównerwowych wêdruj¹cych pomiêdzy komórkami nerwowymi[84].

Uzyskane wyniki mog¹ zostaæ wykorzystane przy two-rzeniu nowych strategii badañ w in¿ynierii tkankowej maj¹-cych na celu przywrócenie po³¹czeñ pomiêdzy uszkodzo-nymi komórkami nerwowymi b¹d polepszenie przekazy-wania sygna³ów nerwowych. Niezbêdne jest jednak posze-rzenie aktualnej wiedzy na temat tego rodzaju materia³óworaz ich oddzia³ywania z komórkami nerwowymi w hodow-lach "in vitro", przed zastosowaniem dla regeneracji uk³adunerwowego zwierz¹t i ludzi.

Zakoñczenie

Obecny stan wiedzy nad regeneracj¹ obwodowego uk³a-du nerwowego pozwala na uzyskanie pozytywnych wyni-ków regeneracji nerwu przy u¿yciu sztucznych implantów.Czêæ wykorzystywanych materia³ów dziêki wynikom rege-neracji porównywalnym z przeszczepami z nerwów skór-nych znajduje ju¿ zastosowanie w leczeniu ludzi. Mimo tokonieczne s¹ dalsze badania weryfikuj¹ce dotychczasowystan wiedzy oraz pozwalaj¹ce na poprawienie uzyskiwa-nych obecnie wyników leczenia.

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[21] Ch.R. Noback, J. Husby, J.M. Girado, C. Andrew, L. Bassett,J.B. Campbell "Neural regeneration across long gaps in mamma-lian peripheral nerves: Early morphological findings.", Anat Rec131 (1958) 633-647.[22] J.M. L. Beau, M.H. Ellisman, H.C. Powell "Ultrastructural andmorphometric analysis of long-term peripheral nerve regenerationthrough silicone tubes." , Journal of Neurocytology 17, 161-172(1988).[23] R.D. Madison, S.J. Archibald "Point Sources of Schwann CellsResult in Growth into a nerve Entubulation Repair Site in the Ab-sence of Axons: Effects of Freeze-Thawing.", Experimental Neu-rology, 128, 266-275 (1994).[24] M. Cuadros-Romero, A. Trueva "Nerve Regeneration UsingPolyglicolic Acid As Alternative To Grafting". The Journal Of HandSurgery Vol 28b Suplment 1.[25] X. Navarro, E. Verdú, F.J. Rodriguez, D. Ceballo "Artificial nervegraft for the repair of peripheral nerve injuries." s; Neurol Sci (2001)22: S7-S13.[26] L.J. Chamberlain, I.V. Yannas, A. Arrizabalaga, H.-P. Hsu, T.V.Norregaard, M. Spector "Early peripheral nerve healing in colla-gen and silicone tube implants: Myofibroblasts and the cellular re-sponse.", Biomaterials 19(1999) 1393-1403.[27] Q. Zhao, L.B. Dahlin, M. Kanje, G. Lundborg "Repair of thetransected rat sciatic nerve: Matrix formation within implanted sili-cone tubes.", Restorative Neurology and Neuroscience, 5 (1993)197-204.[28] J.A. Bertelli, A.R. S. Dos Santos, Joao B. Calixto, J.C. Mira,M.F. Ghizoni "Long interpositional nerve graft consistently inducesincomplete motor nad sensory recovery in the rat. An experimentalmodel to test nerve repair.", Journal of neuroscience methods 134(2004) 75-80.[29] A.I. Gravvanis, A. Ladvas, A.E. Papalois, D.A. Tsoutsos, P.N.Pnayotou, D.C.-C. Chuang, I. Franceschini, M. Dubois-Dalcq, R.Matsas "Collagen tube lined with genetically modified Schwanncells with increased motility: A new promising bioartificial nervegraft"; Eur Surg (2005) 37/4: 204-212.[30] T. Hashimoto, Y. Suzuki, M. Kitada, K. Kataoka, S. Wu, K.Suzuki, K. Endo, Y. Nishimura, C. Ide "Peripheral nerve regenera-tion through alginate gel: analysis of early outgrowth and late in-crease in diameter of regenerating axons."; Exp Brain Re (2002)146: 256-368.[31] I.V. Yannas, B.J. Hill "Seletion of biomaterials for peripheralnerve regeneration using data from the nerve chamber model";Biomaterials 25(2004); 1593-1600.[32]Yueh-Sheng Che, Ching-Liang Hsieh, Chin-Chuan Tsai, Ter-Hsin ChenWen-Chiang Cheng, Cheng-Li Hu, Chun-Hsu Yao "Pe-ripheral nerve regeneration using silicone rubber chambers filledwith collagen, laminin and fibronectin" Biomaterials 21 (2000) 1541-1547.[33] G. Lundborg, L. Dahlin, D. Dohi, M. Kanje, N. Terada "A NewType of "Bioartificial" Nerve Graft for Bridging Extended Defects inNerves" Journal of Hand Surgery (British and European Volume,1997) 22B: 3:299-303.[34] Chen-Jung C., Shan-Hui H. "The Effects Of Low-Intensity Ul-trasound On Peripheral Nerve Regeneration In Poly(Dl-Lactic Acid-Co-Glycolic Acid) Conduits Seeded With Schwann Cells" Ultraso-und In Med. & Biol. 8 (2004) 1078-1084.[35] Y. Katayama, R. Montenegro, T. Freier, R. Midha, J.S. Belkas,M.S. Shoichet "Coil-reinforced hydrogel tubes promote nerve re-generation equivalent to that of nerve autografts" Biomaterials 27(2006) 505-518.[36] C. Sundbacka, T. Hadlockb, M. Cheneyb, J. Vacantia "Manu-facture of porous polymer nerve conduits by a novel low-pressureinjection molding process" Biomaterials 24 (2003) 819-830[37] Nakamura T., Inada Y., Fukuda S., Yoshitani M., Nakada A.,Itoi S., Kanemaru S., Endo K., Shimizu Y. "Experimental study onthe regeneration of peripheral nerve gaps through a polyglycolicacid-collagen (PGA-collagen) tube" Brain Research 1027 (2004)18-29.[38] T. Nakamura, Y. Inada, S. Fukuda, M. Yoshitani, A. Nakada,S. Itoi, S. Kanemaru, K. Endo, Y. Shimizu "Experimental study onthe regeneration of peripheral nerve gaps through a polyglycolicacid-collagen (PGA-collagen) tube, Brain Research 1027 (2004)18-29.

[39] K. Matsumoto, K. Ohnishi, T. Kiyotani, T. Sekine, H. Ueda, T.Nakamura, Ka. Endo, Y. Shimizu "Peripheral nerve regenerationacross an 80-mm gap bridged by a polyglycolic acid (PGA)-colla-gen tube filled with laminin-coated collagen fibers: a histologicaland electrophisiological evaluation of regenerated nerves."; BrainReserch 868 (2000) 315-328.[40] R.A. Weber, W.C. Breidenbach, R.E. Brown, M.E. Jabaley,D.P. Mass "A Randomized Prospective Study of Polyglycolic AcidConduits for Digital Nerve Reconstruction in Humans.", Plast. Re-constr. Surg. 106: 1036, 2000).[41] R. C. Young, M. Wiberg, G. Terenghi "Poly-3-hydroxybutyrate(PHB): a resorbable conduit for long-gap repair in peripheral ne-rves" British Journal of Plastic Surgery 55 (2002) 235-240.[42] A. Hazari, M. Wiberg, G. Johansson-Rudén, C. Green, G. Te-renghi "A resorbable nerve conduit as an alternative to nerve auto-graft in nerve gap repair" British Journal of Plastic Surgery 52(1999) 653-657.[43] Kurita K. "Chemistry and application of chitin and chitosan asfiber and film formers" Polym. Degrad. Stabil. 70 (1998) 7-12.[44] Yuan Y., Zhang P., Yang Y., Wang X., Gu X. " The interactionof Schwann cells with chitosan membranes and fibers in vitro" Bio-materials 25 (2004) 4273-4278.[45] Suzuki T., Mizushima Y."Characterization of silica-chitosancomplex adhesiveness of L-929 cells cultured on the biomembra-ne" J. Ferment Bioeng. 1997;84(2):128.[46] M. R.Ahmed, S. Vairamuthu, Md. Shafiuzama, S. H. Bashad,R. Jayakumar "Microwave irradiated collagen tubes as a bettermatrix for peripheral nerve regeneration" Brain Research 1046(2005) 55 - 67.[47] Ch. Krarup, S.J. Archibald, R.D. Madison."Factors That Influ-ence Peripheral nerve Regeneration: An Elektrophysiological Stu-dy of the Monkey Median Nerve." Ann. Neurol 2002; 51: 69-81[48] S.J. Archibald, J. Shefner, C. Krarup, R.D. Madison "MonkeyMedian Nerve Repair by Nerve Graft or Collagen Nerve GuideTube.", The Journal of Neuroscience, may 1995, 15(5):4109-4123[49] S. Itoh, K. Takakuda, S. Kawabata, Y. Aso, K. Kasai, H. Itoh,K. Shinomiya, "Evaluation of cross-linking procedures of collagentubes used in peripheral nerve repair" Biomaterials 23(2002) 4475-4481[50] S. Yoshii, M. Oka, M. Shima, A. Tanigochi, M. Akagi "30 mmregeneration of rat sciatic nerve along collagen filaments."; BrianReserch 949 (2002) 202-208[51] D.Y. Lee, B.H. Choi, Jh Park, Sj Zhu, By Kim, Jy. Huh, Sh.Lee, Jh. Jung, Sh. Kim "Nerve Regeneration With The Use Of APoly(L-Lactide-Co-Glycolic Acid)-Coated Collagen Tube Filled WithCollagen Gel" Journal Of Cranio-Maxillofacial Surgery (2006) 34,50-56.[52] Kiyotani T., Teramachi M., Takimoto Y., Nakamura T., Shimi-zu Y., Endo K. "Nerve regeneration across a 25-mm gap bridgedby a polyglicolic acid-collagen tubes: a histological and electro-physiological evaluation of regenerated nerves" Brain Research740 (1996) 66-74.[53] Archibald S.J., Krarup C., Shefner J., Li S., Madison R.D. "Acollagen-based nerve guide conduit for peripheral nerve repair: Anelectrophysiological study of nerve regeneration in rodents and non-human primates", J. Comp. Neurol. 306 (1991) 685-696.[54] N. B., Chauhan, H.M. Figlewicz, T.Khan "Carbon filamentsdirect the growth of postlesional plastic axons after spinal cord in-jury" PII: S0736-5748(1999)00003-9.[55] G. Keilhoff, F. Stang, G. Wolf, H. Fansa, Bio-compatibility oftype I/III collagen matrix for peripheral nerve reconstruction, Bio-materials 24 (2003) 2779- 2787.[56] S. Yoshii , M. Oka , M. Shima , A. Taniguchi , M. Akagi "30 mmregeneration of rat sciatic nerve along collagen filaments" BrainResearch 949 (2002) 202-208[57] Bunting S., L. Di Silvio, Deb S., Hall S. "Bioresorbable glassfibres facilitate peripheral nerve regeneration" Jurnal of Hand Sur-gery 3(2005)242-247.[58] B. Balakrishnana, M. Mohantyb, P.R. Umashankarc, A. Jay-akrishnana "Evaluation of an in situ forming hydrogel wound dres-sing based on oxidized alginate and gelatin.", Biomaterials 26 (2005)6335-6342.[59] J.A. Rowley, G. Madlambayan, D.J. Mooney "Alginate hydro-gels as synthetic extracellular matrix materials."; Biomaterials 20(1999) 45-53.

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[73] A.K. Gulati, D.R. Rai, A. M. Ali "The influence of culturedSchwann cells an regeneration through acellular basal lamina gra-fts."; Brain Research 705 (1995) 118-124.[74] Heiduschka P., Thanos S. "Implantable bioelectronic interfa-ces for loset nerve function" Progress in Neurobiology 55 (1998)433-461.[75] Lago N.,Ceballos D.,Rodriguez F.J. Stieglitz T., Navarro "Longterm assessment of axonal regeneration through polyimide rege-nerative electrodes to interface the peripheral nerve" Biomaterials26 (2005) 2021-2031.[76] Akin T., Najafi K., Smoke R.H., Bradley R.M. " A micromachi-ned silicon sieve electrode for nerve regeneration applications"Transactions of Biomedical Engineering 41 (1994)[77] Navarro X, Calvet S, But!i M, G!omez N, Cabruja E, Garrido P,Villa R, Valderrama E. Peripheral nerve regeneration through mi-croelectrode arrays based on silicon technology. Restor NeurolNeurosci 1996;9:151-60.[78] Zhao Q, Drott J, Laurell T, Wallman L, Lindstr.om K, BjurstenLM, Lundborg G, Montelius L, Danielsen N. "Rat sciatic nerve re-generation through a micromachined silicon chip" Biomaterials 18(1997) 75-80.[79] Navarro X, Calvet S, Rodr!iguez FJ, Stieglitz T, Blau C, But!iM, Valderrama E, Meyer JU. "Stimulation and recording from rege-nerated peripheral nerves through polyimide sieve electrodes" JPeripher Nerv System 2 (1998) 91-101.[80] X. Zhang, S. Prasad, S. Niyogi, A. Morgan, M. Ozkan, C. S.Ozkan "Guided neurite growth on patterned carbon nanotubes"Sensors and Actuators B 106 (2005) 843-850[81] M. Tatagiba, C. Brosamle, M.E. Schwab, Regeneration of in-jured axons in the adult mammalian central nervous system, Neu-rosurgery 40 (3) (1997) 541.[82] J.L. McKenzie, M.C. Waid, R. Shi, T.J. Webster " Decreasedfunctions of astrocytes on carbon nanofiber materials" Biomate-rials 25 (2004) 1309-1317[83] Roche Stephan "Carbon nanotubes: exceptional mechanicaland electronic properties",nn. Chim. Sci. Mat, 2000, 25, pp.529-532.[84] Telford M. "Carbon nanotubes boost neural signaling" Rese-arch News 2005.

[60] M. Martins-Green"The dynamics of cell-ecm interactions, withimplications for tissue engineering" Department of Biology, Uni-versity of California, Riverside, Ca 92521.[61] E. Ruoslahti "RGD and other recognition sequences for inte-grins", Annu. Rev. Cell Dev. Biol. 1996, 12: 697-715.[62] Y. Suzukia, M. Taniharab, K. Ohnishic, K. Suzukia, K. Endod,Y. Nishimuraa "Cat peripheral nerve regeneration across 50 mmgap repaired with a novel nerve guide composed of freeze-driedalginate gel"; Neuroscience Letters 259 (1999) 75-78.[63] Labrador RO, Buti R, Navarro X "Influence of collagen andlaminin gels concentration on nerve regeneration after resectionand tube repair" Exp Neurol 149: 243-252, 1998.[64] I. H. Whitworth, R. A. Brown, C. J. Dore, P. Anand, C. J. Gre-en, G. Terenghi "Nerve Growth Factor Enhances Nerve Regene-ration Through Fibronectin Grafts" Journal of Hand Surgery (Bri-tish and European Volume, 1996) 2lB." 4:514-522.[65] Hollowell JP, Villadiego A, Rich KM. "Sciatic nerve regenera-tion across gaps within silicone chambers: long-term e!ects of NGFand consideration of axonal branching" Exp Neurol 1990;110: 45-51.[66] Pei-Ru Chena, Ming-Hong Chena, Jui-Sheng Sunc, Mei-HsiuChend, Chien-Chen Tsaie, Feng-Huei Linf "Biocompatibility of NGF-grafted GTG membranes for peripheral nerve repair using culturedSchwann cells" Biomaterials 25 (2004) 5667-5673.[67] Hurtado A., Moon L.D.F., Maquet V., Blits B., Jerome R., Oude-ga M. "Poly (D,L-lactic acid) macroporous guidance scaffolds se-eded with Schwann cells genetically modified to secrete a bi-func-tional neurotrophin implanted in the completely transected adultrat thoracic spinal cord" Biomaterials 27(2006)430-442.[68] Ide C. "Peripheral nerve regeneration" Neurosci Res 1996;25:101-21.[69] Gulati AK, Rai DR, Ali AM. Influence of cultured Schwann cellson regeneration through acellular basal lamina grafts. Brain Res1995;705:118-24.[70] E. O. Johnson, A. B. Zoubos, P. N. Soucacos "Regenerationand repair of peripheral nerves" Injury 36S (2005) S24-S29.[71] Campbell YZ, Anderson PN, Martini R, Schachner M, Lieber-man AR. Molecular basis of interactions between regenerating adultrat thalamic axons and Schwann cells in peripheral nerve grafts I.Neural cell adhesion molecules. J Comput Neurol 1995; 361:193-209.[72] C. Ide, K. Tohyama, K. Tajima, K. Endoch. K. Sano, M. Tamu-ra, A. Mizoguchi, M. Kitada, T. Morihara, M. Shirasu "Long Acellu-lar Nerve Transplants for Allogeneic Grafting and the Effects ofbasic Fibroblast Growth Factor on the Growth of Regenerating Axo-na in Dogs: A Preliminary Report."; Experimental Neurology 154,99-112 (1998).

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DESIGN OF RESORPTIONPROPERTIES OF THE METALBONE IMPLANTS APPLICATIONIN VIVO

FRIEDRICH-WILHELM BACH*, RAFAEL KUCHARSKI*,DIRK BORMANN*,DIETER BESDO**, SILKE BESDO**,CHRISTIAN HACKENBROICH***, FRITZ THOREY****,ANDREA-MEYER-LINDENBERG***

* INSTITUTE OF MATERIALS SCIENCE, SCHÖNEBECKER ALLEE 2,30823 GARBSEN, GERMANY

** INSTITUT FÜR KONTINUUMSMECHANIK, APPELSTRAßE 11, 30167HANNOVER, GERMANY

***DEPARTMENT OF ORTHOPAEDIC SURGERY, HANOVER MEDICAL

SCHOOL, HANOVER, GERMANY

****CLINIC FOR SMALL ANIMALS, UNIVERSITY OF VETERINARY

MEDICINE HANOVER, FOUNDATION, GERMANY


Abstract

The purpose of the dissertation was to optimize thecasting method of producing the magnesium alloy im-plants for the purpose of filling bone defects. Charac-teristics of the resulting material structure were testedusing computer micro-tomography. Also themechanical properties were tested. The results ob-tained had a direct impact on the design of the size ofpores and thickness of internal walls of the spongymetallic materials. The dissertation also presents themethodology and results of the testing adhesion ofthe animal femoral bone in vivo. The evaluation of thebone reconstruction was performed using the methodof four-point bending. The tests were carried out onthe New Zealand Rabbit experimental animals. Firststage of the tests concerned measuring of the stiff-ness in vivo, in which the PLA control materials wereused. The research results obtained in vivo set outthe possibilities of designing resorbing structureswith open pores derived on the basis of magnesiumalloys for the purpose of the application inthe bone surgery as filling materials for bone defects.Key words: magnesium sponges, manufacturingmethod, quality control, in vivo research, mechanicalproperties examination


Introduction

Applying new osseous implants based on magnesiumalloys brings new possibilities in bone losses treatment. Dueto possibility of controlled resorption in physiologic fluids, inthe nearest future magnesium alloys will be applied as amaterial for temporary implants [1,2]. These implants afterhaving fulfilled their stabilising and curing purpose, are natu-rally removed (resorbed) from the organism[3,4]. This fea-ture, apart from wholesome advantages for the patient, alsobrings financial savings, due to avoiding the reimplantationintervention[5]. Based on resorbing magnesium alloy, astructure with open pores and solid outer layer was cre-ated. This structure is patterned upon spongiosis andkortikalis of the natural bone. To examine the influence ofthe implanted material on the bone healing process, oste-otomy interventions were carried out on shank bones of

PROJEKTOWANIE W£ASNOCIRESORBOWALNYCH,METALICZNYCH IMPLANTÓWKOSTNYCH ZASTOSOWANIEW WARUNKACH IN VIVO

FRIEDRICH-WILHELM BACH*, RAFAEL KUCHARSKI*,DIRK BORMANN*,DIETER BESDO**, SILKE BESDO**,CHRISTIAN HACKENBROICH***, FRITZ THOREY****,ANDREA-MEYER-LINDENBERG***

* INSTITUTE OF MATERIALS SCIENCE, SCHÖNEBECKER ALLEE 2,30823 GARBSEN, GERMANY

** INSTITUT FÜR KONTINUUMSMECHANIK, APPELSTRAßE 11, 30167HANNOVER, GERMANY

***DEPARTMENT OF ORTHOPAEDIC SURGERY, HANOVER MEDICAL

SCHOOL, HANOVER, GERMANY

****CLINIC FOR SMALL ANIMALS, UNIVERSITY OF VETERINARY

MEDICINE HANOVER, FOUNDATION, GERMANY


Streszczenie

Celem pracy by³o okrelenie stopnia zrostu zwie-rzêcej koci udowej w warunkach in vivo. Badaniaprzeprowadzono poprzez wykorzystanie metody ba-dania stopnia sztywnoci w warunkach wzrostu war-toci si³y w czteropunktowym ugiêciu. Do badania za-kwalifikowano grupe zwierzat doswiadczalnych rasykrólik nowozelandzki (New Zeland Rabit). W pierw-szej fazie badañ jak wszczepy zastosowano materia-³y kontrolne z PLA. Wyniki badañ okrelaj¹ zarysmo¿liwoci zastosowania w chirurgii kostnej materia-³ów na ubytki kostne wykonanych z resorbowalnychstruktur na bazie stopów magnezu. W pracy przed-stawiono ponadto metodykê wytwarzania oraz kon-trole jakoci procesu wytwarzania struktur magnezo-wych z porami otwartymi z zastosowaniem na implantyw chirugii kostnej. Tak okrelone materia³y implanta-cyjne zostan¹ przebadane w drugiej fazie badañ wwarunkach in vivo metoda okrelenia stanu sztywno-sci w czteropunktowym ugiêciu. Badania umo¿liwi¹pe³ne okrelenie wp³ywu implantów na czas i warunkiosteosyntezy.

S³owa kluczowe: g¹bki magnezowe, metodykawytwarzania, kontrola jakoci, badania w warunkachin vivo, badania w³asnoci mechanicznych.


Wstêp

Zastosowanie nowych implantów kostnych wytworzonychna bazie stopów magnezu stwarza nowe mo¿liwoci dlaleczenia ubytków kostnych. Stopy magnezu poprzez mo¿-liwoæ kontrolowanej resorpcji w warunkach pracy w p³y-nach fizjologicznych w najbli¿szej przysz³oci znajd¹ za-stosowanie kliniczne jako materia³ na implanty czasowe[1,2]. Implanty te po spe³nieniu swojej funkcji stabilizacyj-no-leczniczej zostaj¹ w sposób naturalny usuniête (resorp-cja) z organizmu [3,4]. Powy¿sza w³aciwoæ stwarza opróczzalet zdrowotnych dla pacjenta tak¿e oszczêdnoci finan-sowe zwi¹zane z ominiêciem zabiegu reimpaltacji[5]. Nabazie materia³u resorbowalnego, jakim s¹ stopy magnezuwytworzono strukturê z porami otwartymi z zewnêtrzn¹ war-stw¹ lit¹ wzoruj¹c siê na spongiozie i kortikalis koci natu-

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ralnej. Aby zbadaæ wp³yw zaimplantowanego materia³u naproces leczenia koci przeprowadzono u dowiadczalnychosobników królika zabieg osteotomii koci podudzia (Tibiae)z udzia³em implantu oraz bez udzia³u implantu.

Pomiar sztywnoci wykonywano w czasie ca³ego proce-su leczenia w warunkach in vivo okrelaj¹c wartoci si³ wczteropunktowym ugiêciu.

Materia³ i metody

Metaliczne struktury z porami otwartymi wykonano me-tod¹ odlewnicz¹ stosuj¹c wype³niacz ceramiczny. Jakowype³niacz zastosowano cz¹stki NaCl o wielkoci 250 i500µm. Jako materia³u infiltruj¹cego zastosowano stopymagnezu. Po³¹czenia materia³ów dokonano metoda odlew-nicza infiltruj¹c cz¹stki soli ciek³ym metalem [6,7,8].

Otrzymany kompozyt: cz¹stki ceramiczne w osnowie sto-pu magnezu, przygotowano do nieniszcz¹cych badañ kon-troli jakoci stopnia infiltracji. W tym celu wykonano cylin-dryczne próby o wysokoci 10mm i rednicy 8mm w se-riach z odlewów z piêciu stopów magnezu. Otrzymane wten sposób cylindry przebadano metod¹ radiologiczn¹ wurz¹dzeniu µCT firmy Scanco Medical. W celu dok³adniej-szej kontroli jakoci wybranych cylindrów zastosowano me-todê mikroskopii skaningowej Mikroskopem Firmy Jeolprzed i po chemicznym wyp³ukaniu fazy ceramicznej.

Ocenê wytrzyma³oci mechanicznej porowatych struk-tur przeprowadzono stosuj¹c metodê ciskania z jednostaj-n¹ prêdkoci¹ zgniotu (aparatura f-my Zwick) (RYS.3).

U wybranych przedstawicieli zwierz¹t dowiadczalnychwykonano zabieg osteotomii prawej koci piszczelowej.Zabieg osteotomii zosta³ przeprowadzony przy wspomaga-

experimental rabbit individuals with and without applicationof the implant. The rigidity measurements were taken dur-ing the whole process of healing in in vivo condidions. Inthe measurements force values were determined for four-point deflection.


Metallic structures with open pores were created usingfounding methods with ceramic filling. The filling were theNaCl particles of 250µm and 500µm size. The infiltratingmaterial was the magnesium alloy. The materials mergingwas made with founding methods, infiltrating salt particleswith the liquid metal [6,7,8].

The obtained composite: ceramic particles In metallicmatrix has been prepared for nondestructive quality controland the degree of infiltration. For this purpose, cylindric sam-ples od 10 mm height and 8 mm diameter were manufac-tured in series of casting of five magnesium alloys. Theobtained cylinders have been examined using radiologicmethods in the Sanco Medical µCT device. For more pre-cise control of selected cylinders, a scanning microscopemethod was applied with use of the JEOL microscope be-fore and after chemical washing the ceramic phase out.

The mechanic strength of porous structures assessmenthas been taken using the method of compression withsteady speed of deformation

On selected experimental animal individuals an osteotomyintervention on right tibia bone was carried out. The interven-tion was uniplanetary aided with internal stabilizers.

For measurements, the stabilizers hale been dismantled.This allowed measuring the fracture during the entire proc-ess of healing with no influence of external agent (externalstabilizer)

The aim of the research was to compare the influence ofbone implants based on magnesium alloys and PLA implantson bone fracture healing. Until now, the research was car-ried out on a group of experimental animals without implantsin osteotomy region and a group of animals with PLApolyactide control bars. The group of animals with magne-sium bar implants will be examined in the further stage ofresearch. First examinations were carried out 4 weeks afterthe implantation. During 6-7 weeks, twice a week force meas-

RYS. 1.FIG. 1.

RYS. 3. G¹bka wykonana ze stopu magnezu wposzczególnych fazach badania odpornoci naciskanie.artymi.FIG. 3. Sponge made of magnesium alloy inseveral phases of compressive strength

RYS. 2. a) Obraz kompozytu metal-ceramika wformie odlewniczej.b) Obraz struktury z porami otwartymi.FIG. 2. a) Metal-ceramic composite in castingmould.b) Open pore structure.

a) b)

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urements in four-point deflection were made.The anesthetized animals lying in ventral position on a

specially adapted operating table were subjected to oste-otomy intervention. The right hindlimb was held from a kneejoint to a hip joint (FIG. 6).

Force measurement was carried out after adjusting the ap-propriate load by the device transmitting the load to the barsfixing the external stabilizer closest to the osteotomy region.

niu unipalnetarnym ze stabilizatorem zewnêtrznym.W czasie przeprowadzenia pomiaru zdemontowano sta-

bilizator. Umo¿liwia³o to wykonanie pomiaru fraktury w cza-sie ca³ego procesu leczenia bez wp³ywu czynnika dodatko-wego (stabilizator zewnêtrzny).

Celem badania by³o porównanie wp³ywu wszczepianychimplantów kostnych wytworzonych na bazie stopów magne-zu i implantów z PLA na leczenie fraktury koci.

Do chwili obecnej badaniom poddano grupê dowiad-czalnych zwierz¹t bez implantu w przedziale osteotomii orazgrupê zwierz¹t z wszczepami prêtów kontrolnych wykona-nych z polilaktydu PLA. Grupa zwierz¹t z wszczepami zprêtów magnezowych zostanie przebadana w dalszym eta-pie dowiadczeñ. Pierwsze badania przeprowadzono po 4tygodniach od momentu zabiegu implantacyjnego. Przezokres 6-7 tygodni dwa razy w tygodniu wykonywano bada-nia pomiaru si³y w czteropunktowej próbie ugiêcia.

Zwierzêta pod narkoz¹, le¿a³y w pozycji brzusznej nazaadoptowanym do tego badania stole operacyjnym i pod-dane zosta³y zabiegowi osteotomii. Prawa koñczyna dolnazosta³a podtrzymana od stawu kolanowego do stawu bio-drowego (RYS. 6).

Pomiar si³ przeprowadzano dostosowuj¹c odpowiednieobci¹¿enie przez przyrz¹d przenosz¹cy nacisk do prêtówmocuj¹cych stabilizator zewnêtrzny, po³o¿onych najbli¿ejmiejsca osteotomii. Stanowisko pomiarowe umo¿liwia³ozmianê zadanego obci¹¿enia w przedziale co 25g. Na po-cz¹tku dowiadczenia maksymalne obci¹¿enie wynosi³o100g. W ci¹gu dalszego procesu leczenia wielkoæ obci¹-¿enia wzros³a do 500g.

Wyniki pomiaru naprê¿eñ i wartoci ugiêcia zosta³y za-rejestrowane dla ka¿dej z grup badanych zwierz¹t.

Wyniki

W procesie odlewniczym (RYS.7) otrzymano strukturymagnezowe o gradientowym roz³o¿eniu pór otwartych.

Kontrolê jakoci otrzymanych struktur metalicznych nabazie piêciu wybranych stopów magnezu przeprowadzonostosuj¹c dwie metody. W metodzie pierwszej do oceny wy-tworzonych struktur z porami otwartymi u¿yto metody okre-lenia naprê¿enia w stosunku do odkszta³cenia Pierwszametoda badañ kontroli jakoci otrzymanego wyrobu pole-ga³a na scharakteryzowaniu struktur g¹bczastych poprzezwykrelenie zale¿noci krzywej wartoci odkszta³cenia wstosunku do wartoci naprê¿enia metod¹ pomiaru wytrzy-ma³oci na ciskanie (RYS.8).

W ka¿dej z przeprowadzonych prób okrelono w prze-dziale odkszta³cenia 10-20% charakterystyczn¹ wartoæplato dla materia³ów porowatych niezale¿n¹ od u¿ytego

RYS. 5. Schemat warunków przeprowadzeniabadañ w czteropunktowym ugiêciu.FIG. 5. Scheme for conditions of four-pointdeflection research.

RYS. 7. Struktura z porami otwartymi przedusuniêciem wype³nienia ceramicznego zzewnêtrzn¹ warstw¹ lit¹ wykonan¹ na wzór kocinaturalnej.FIG. 7. Structure with open pores before removingthe ceramic filling with solid outer layer, patternedupon a natural bone.

RYS. 8.FIG. 8.

RYS. 6.FIG. 6.

RYS. 4.FIG. 4.

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The measurement station allowed changing the loadevery 50 grams. In the beginning of the experiment, themaximal load was 100 grams. During the healing processthe value of load raised up to 500 grams. Tension meas-urement results and deflection values were recorded foreach of the examined animals group.

Results

In the casting process (RYS. 7) magnesium structuresof gradient distribution of open pores were obtained.

The quality control of the metallic structures based onfive magnesium alloys was carried out with the use of twomethods. In the first case, for assessment of the structureswith open pores a method of determining tension in relationto distortion was used (FIG. 8).

In every test, within 10-20% distortion a characteristic valueof plateau for porous materials, independent on the materialused was determined. The following ASTM alloys were used:AM 20, AE 42, AM50, AM60 and pure magnesium.

Due to advantages of non-destructive examinations, aswell as the short time of the very examination, a computerassisted microtomography method has been chosen. Themethod was applied for examining the state of the magne-sium alloy with the ceramic filling and after removing thefilling. The CAmT examination allows precise determiningcontent of the ceramic filling in the magnesium sponge. Lackof qualitive examinations in this stage of manufacturing maycause the product to be useless during resorption time re-search. Ceramic NaCl filling in water solution causes for-mation of local corrosion centres, which disqualify the ma-terial as a filling of bone losses.

The research on rigidity state (RYS. 11) reveals that dur-ing the osteotomy healing the value of bone rigidity in-creases. Also a relation between the force value and de-flection for low linear loads is visible.

The calculations of deflection forces obtained in the upto the present research as functions determining effective-ness of healing of the fracture reveal results to be scat-tered. After plotting the third degree polynomial trend line,the following rule is wisible: The rigidity increases, then sta-bilizes and finally increases again.

Discussion

Using foundry methods, magnesium alloy porous struc-tures were obtained. Optimizing the foundry process as-

materia³u.Do badañ u¿yto stopów wg ASTM czystego magnezu

oraz jego stopów: AM 20, AE 42, AM50, AM60.Jako drug¹ metodê kontroli jakoci, z uwagi na zalety

badañ nieniszcz¹cych jak i czas wykonania samego bada-nia, wybrano metodê mikrotomografii komputerowej.

Badaniu poddano odlew stopu magnezu z wype³niaczemceramicznym oraz odlew po usuniêciu chemicznie wype³-niacza (RYS. 9 i 10).

Badanie mikro-CT pozwala na dok³adne okrelenie za-wartoci wype³niacza ceramicznego w g¹bce magnezowej.Brak badañ jakociowych na tym etapie procesu wytwarza-nia mo¿e wykazaæ bezu¿ytecznoæ produktu w czasie dal-szych badañ czasu resorpcji. Wype³nienie ceramiczne NaClw roztworze wodnym prowadzi do lokalnych ognisk koro-zyjnych dyskwalifikuj¹cych omawiany materia³ jako wype³-nienie ubytków kostnych.

Z badañ stanu sztywnoci (RYS.12 ) wynika, i¿ w czasieleczenia osteotomii wartoæ sztywnoci koci wzrasta. Wi-doczny jest równie¿ zwi¹zek pomiêdzy wartoci¹ si³y a ugiê-ciem, dla niewielkich obci¹¿eñ o przebiegu liniowym.

Obliczenia wartoci si³ ugiêcia uzyskanych w dotychcza-sowych badaniach jako funkcje wyznaczaj¹ce skutecznoæleczenia z³amania wykazuj¹ rozrzut wyników

Wykrelaj¹c liniê trendu wed³ug polynomu trzeciego stop-nia widoczna jest nastêpuj¹ca prawid³owoæ: wartoæ sztyw-noci wzrasta by póniej ulec stabilizacji a nastêpnie zno-wu wzrastaæ.

Dyskusja

Sposobem odlewniczym otrzymywano struktury porowa-te na bazie stopów magnezu. Optymalizacja procesu od-

RYS. 9.FIG. 9.

RYS. 10.FIG. 10.

RYS. 11. Wykres wartoci si³y w stosunku dowartoci osi¹gniêtego ugiêcia u królika numer316364 w okresie leczenia uszkodzenia kostnego.FIG. 11. Force in relation to deflection. Rabbit No316364 during healing the bone damage.

RYS. 12. Obliczenia wartoci si³ ugiêciauzyskanych w dotychczasowych badaniach jakofunkcje wyznaczaj¹ce skutecznoæ leczeniaz³amania.FIG. 12. Calculations of the forces of deflectionobtained on the up to present research asfunctions determining effectiveness of healing thefracture.

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sures repeatability and high quality of the obtained magne-sium sponges. To characterize the obtained sponges, thematerial has been subjected to mechanical compressionstrength tests. The test in some way simulates conditionsof future sponge performance in the organism. Quality con-trol of the implant allows, thanks to Cant, optimizing themanufacturing process for the magnesium sponges.

The examination of rigidity with the use of four-point de-flection marks the increase of rigidity in all cases of the ex-amined animals. The scatter of the results may be the ef-fect of anatomic differences of every individual. Moreover,it has been observed, that for almost half of the animalswith the PLA bars implanted the rigidity increase was fasterthan for the control animals without the PLA bars. The re-sults presented above show positive influence of biodegrad-ing implants on the process of bone healing. This allowsassuming, that applying porous metallic structures basedon magnesium alloys as temporary implants will influencethe significant increase of bone rigidity and thus hasting thehealing process.

Acknowledgements

The authors wish to tank for hel pand suport to the Ger-man Scientific Collectivity.

MAGNESIUM COMPOUNDSTRUCTURESFOR THE TREATMENT OF BONEDEFECTS

FRIEDRICH-WILHELM BACH, RAFAEL KUCHARSKI, DIRK BORMANN

INSTITUTE OF MATERIALS SCIENCE,SCHÖNEBECKER ALLEE 2, 30823 GARBSEN, GERMANY


Abstract

The dissertation demonstrates possibilities of pro-ducing one-phase compound structures on the basisof magnesium alloys composed of solid material, par-tially or wholly wrapped in the porous external layer.

Compound moulders were produced using the cast-ing method with the application of ceramic filler (NaCl)infiltration. Characteristics of the compounds obtained

lewniczego zapewnia powtarzalnoæ i wysok¹ jakoæ uzy-skanych g¹bek magnezowych. Celem charakteryzacji otrzy-manych g¹bek magnezowych materia³ poddano badaniommechanicznym w próbie wytrzyma³oci na ciskanie. Pró-ba czêciowo symuluje warunki póniejszej pracy g¹bekmagnezowych jako implanty na wype³nienia ubytków kost-nych w organizmie. Kontrola jakoci wykonania implantówdziêki technice µCT pozwalaj¹ na optymalizacjê procesuwykonania g¹bek magnezowych.

Badania sztywnoci koci metod¹ czteropunktowegougiêcia wskazuj¹ na wzrost wartoci sztywnoci u wszyst-kich przebadanych zwierz¹t. Rozrzut wyników mo¿e byæefektem ró¿nic anatomicznych u poszczególnych osobni-ków. Ponadto zaobserwowano, ¿e przy blisko po³owie prze-badanych zwierz¹t z wszczepionymi prêtami wykonanymiz PLA wzrost wartoci sztywnoci ugiêcia nastêpowa³ szyb-ciej ni¿ u zwierz¹t kontrolnych bez prêtów z PLA. Powy¿-sze wyniki wskazuj¹ na korzystny wp³yw biodegradowal-nych implantów na proces zrastania siê koci. Pozwala tos¹dziæ, ¿e zastosowanie porowatych struktur metalicznychna bazie stopów magnezu jako implantów czasowych bê-dzie wp³ywaæ na znaczny wzrost wartoci sztywnoci kocia tym samym na przyspieszenie przebiegu leczenia.

Podziêkowania

Autorzy dziêkuj¹ za pomoc i wsparcie Niemieckiej Wspól-nocie Naukowej.

MAGNEZOWE STRUKTURYHYBRYDOWE W ZASTOSOWANIUNA LECZENIE UBYTKÓWKOSTNYCH

FRIEDRICH-WILHELM BACH, RAFAEL KUCHARSKI, DIRK BORMANN

INSTITUTE OF MATERIALS SCIENCE,SCHÖNEBECKER ALLEE 2, 30823 GARBSEN, GERMANY


Streszczenie

W pracy wykazano mo¿liwoæ wytwarzania hybry-dowych struktur sk³adaj¹cych siê z litego materia³uoraz otaczaj¹cych jego powierzchnie ugrupowañ zmateria³u porowatego z porami otwartymi wytworzo-nych na bazie stopów magnezu. Otrzymane w tensposób struktury wytworzono metoda odlewnicza in-filtruj¹c wype³nienie ceramiczne. Przedstawiono ko-

References[4] Gro2003 Offenporige Metallstrukturen nach dem Platzhalterver-fahren.[5] Bach Fr.-W., Bormann D., Kucharski R., Wilk P.: Productionand Properties of Foamed Magnesium; Cellular Metals and Poly-mers, Eds.: R. F. Singer, C. Körner, V. Altstädt, H. Münstedt, TransTech Publications, Zuerich 2005, S. 77-80.[7] Bach Fr.-W., Bormann D., Kucharski R. November Colloquium2005.[8] Bach F, Bormann D., Kucharski R., Jendras M., Windhagen M.,Hackenbroich Ch., Krause A., Meyer-Lindenberg A. "Resorbowal-ne, metaliczne implanty kostne".

Pimiennictwo

[1] Hayes, W.C.; Bouxsein, M.L.: Biomechanics of Cortical and Tra-becular Bone:Implications for Assessment of Fracture Risk. In: BasicOrthopaedic Biomechanics, Editors: Mow,V.C.; Hayes, W.C. Lip-pincott-Raven Publishers, Philadelphia, 1997[2] Nie2004 Unterlagen zur Vorlesung "Biokompatible Werkstof-fe", PD Dr.-Ing. M. Niemeyer, 2004[3] Kam+2000 Magnesium Taschenbuch, Aluminium-VerlagDüsseldorf, 2000

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were tested using the scanning electron microscopySEM (analysis of microstructure) and non-destruct-ing 3D model analysis performed using computer mi-cro-tomography.

The purpose of the compound structure was toenhance properties through using of the solid mate-rial and extending the resorption period of the moulder,compared to the spongy resorbing magnesium mate-rials currently produced.

Thus obtained compound structures can be usedas a new material in the treatment of the bone defectsboth in the long and flat bones.

Key Words: magnesium sponges, porous hybridstructures, manufacturing methods, quality control.


Introduction

Application of new bone implants based on magnesiumalloys brings new possibilities in bone losses treatment [1],[2]. Thanks to temporal properties, revealing during opera-tion in vivo magnesium alloys can be qualified as a boneloss filling material. Yet, due to not optimised resorption time,they cannot be applied in clinical conditions. One of themethods, improving this inconvenience is manufacturinghybrid structures. These, based on the same core - onmagnesium alloy as a monophase material should be char-acterized by fair mechanical properties. The idea ofmonophase hybrid structure leans upon linking the solidmaterial with the open pore one with a metallic bond. Thanksto this connection, an open pore properties are obtained.These allow physiologic fluids flow as well as fixing withnatural bone. The solid material, in turn, brings greater pos-sibilities of building the skeleton for load bearing, enhanc-ing the development of natural metabolism of the osseoussystem. [5], [6]. This brings new possibilities for applyingthe magnesium alloys, which, as temporary implants maybe used in vast systems of bone fillings, not available forsponges of only porous structure so far. Magnesium prop-erties have been presented in TABLE 1.


Metallic hybrid structures with open pores were madewith use of foundry methods with application of ceramic fill-ing. As a ceramic filling NaCl particles of 250µm and 500µmsize were used. As an infiltrating material, due to its castingproperties an AZ91 magnesium alloy has been used as aprecursor. This alloy consists of 9% Al and about 1% Zn.Materials were fixed with casting methods by infiltration ofsalt particles with and without the elements of the samealloy with liquid AZ91 metal.

From the composite: ceramic particles in magnesium

lejne fazy wytworzenia struktur hybrydowych oraz ichcharakterystykê wykorzystuj¹c badania mikrostrukturyw elektronowej mikroskopii skaningowej (SEM - ska-ning elektrony microscopy) oraz nienieszczace bada-nia modelowe w skali 3D uzyskane dziêki zastoso-waniu mikrotomografii komputerowej.

Cel wytworzonej struktury hybrydowej zosta³ okre-lony zarówno jako wzmocnienie mechaniczne wy-konane przez kszta³tkê z litego materia³u jak równie¿przed³u¿enie czasu resorpcji kszta³tki w porównaniudo wytwarzanych obecnie magnezowych materia³ówresorbowalnych o strukturze g¹bczastej.

Zastosowanie tak wykonanych struktur hybrydo-wych okrelono jako nowe tworzywa w leczeniu ubyt-ków kostnych zarówno w kociach d³ugich jak i p³a-skich.

S³owa kluczowe: g¹bki magnezowe, hybrydowestruktury porowate, metodyka wytwarzania, kontrolajakoci.


Wstêp

Zastosowanie nowych implantow kostnych wytworzonychna bazie stopow magnezu stwarza nowe mozliwosci dlaleczenia ubytkow kostnych [1, 2].

Dziêki w³aciwoci¹ temporalnym ujawniaj¹cym siê pod-czas pracy w warunkach "in vivo" stopy magnezu posiada-j¹ potencja³ kwalifikuj¹cy je na materia³y na wype³nieniaubytków kostnych. Jednak¿e poprzez nie zoptymalizowa-ny czas resorpcji [3], [4] nie mog¹ do tej pory znaleæ za-stosowania w warunkach klinicznych. Jedn¹ z dróg popra-wiaj¹cych tê niedogodnoæ jest metoda wytwarzania struk-tur hybrydowych. Struktury hybrydowe oparte na tym sa-mym materiale wsadowym - stopie magnezu jako materia-le jednofazowym powinny charakteryzowaæ siê dobrymiw³aciwociami mechanicznymi. Istota jednofazowej struk-tury hybrydowej polega na po³¹czeniu wi¹zaniem metalicz-nym materia³u litego z materia³em otwarto porowatym. Dziêkitemu po³¹czeniu otrzymujemy materia³ z w³aciwociamiotwarto porowatymi pozwalaj¹cymi na przep³yw p³ynów fi-zjologicznych i fiksacjê z naturaln¹ koci¹, materia³ lity na-tomiast daje wiêksze mo¿liwoci w stworzeniu szkieletu doprzenoszeñ obci¹¿eñ u³atwiaj¹c tym samym i wspomaga-j¹c rozwój naturalnego metabolizmu uk³adu kostnego[5], [6].Stwarza to nowe mo¿liwoci dla zastosowania stopów ma-gnezu mog¹cych jako temporalne implanty zostaæ u¿yte nawiêksze systemy wype³nieñ ubytków kostnych bêd¹ce niedostêpne do tej pory dla g¹bek tylko o strukturze otwartoporowatej. W³aciwoci magnezu przedstawiono w TABE-LI 1.

Materia³ i metody

Metaliczne struktury hybrydowe z porami otwartymi wy-konano metod¹ odlewnicz¹ z zastosowaniem wype³niaczaceramicznego. Jako wype³niacza u¿yto cz¹stek NaCl o wiel-kosci 250 i 500 um. Jako materialu inflitrujacego z uwagi naw³aciwoci odlewnicze dla prekursora zastosowano stopmagnezu AZ91, sk³adaj¹cy siê z ok. 9% Al. i ok. 1% Zn.Po³¹czenia materia³ów dokonano metod¹ odlewnicz¹ infil-truj¹c cz¹stki soli wraz z elementami z tego samego stopuoraz bez ciek³ym metalem AZ91.

Z otrzymanego kompozytu: cz¹stki ceramiczne w osno-wie stopu magnezu, usuniêto w procesie chemicznego p³u-kania [7] wype³niacz ceramiczny otrzymuj¹c jednofazow¹strukturê hybrydow¹ z magnezu.

Otrzymane w ten sposob materia³y przebadano meto-TABELA 1.TABLE 1.

Materia³ Material

Masa molekularna Molecular mass

[g/mol]

E-Modul E-Modulus

[GPa]

Wytrzyma³oæ na rozci¹ganie

Strength [MPa]

50000 1,2 28 Poly-L-lactid

100000 2,7 50

Kortikalis - 10-30 110-160 (ciskanie)

Magnesium 24 44 150

Steel 316L 56 200 400

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alloy groundmass the ceramic filling has been removed inchemical rinsing [7]. This way, a monophase magnesiumstructure has been obtained. The obtained structures havebeen examined with radiological methods in a uCT ScancoMedical device (FIG.1c)

For more accurate control, selected cylinders were ex-amined with the scanning Jeol microscope. The examina-tion took place before and after the chemical rinsing.

In order to obtain a homogenous material, and thus link-ing the solid metal with open pore structure, salt mouldsfilled with ceramic filling were made. These were speciallyshaped in order to gather the solid material (FIG.3).

In the further stage of research, different shapes wereprepared in a heated mould with ceramic filling, in order toremove the magnesium oxide layer

Results

As it is shown in FIG. 5, the casting process revealedthat it is possible to obtain a monophase hybrid structurewith this method. It is also possible to obtain structures ofgradient distribution of the open pores. In order to adjustthe method described above for particularapplications,further research is necessary to be carried out.

The quality of the magnesium alloy casting with ceramicfilling has been examined with the use of Computer AidedMicro-Tomography (CAµT). As it is shown in FIG. 5 (withfilling) and 8 (without filling), the CAµT allows precise deter-mination of the ceramic filling content in the magnesiumsponge Lack of qualitive examinations in this stage of manu-facturing may cause the product to be useless duringresorption time research. Ceramic NaCl filling in water so-lution causes formation of local corrosion centres, whichdisqualify the material as a filling of bone losses.Discussion

The quality of the hybrid material has been derived fromthe state of the solid material - open pore structure connec-tion. it seems that the greatest problem is proper sealing ofthe mould and properly chosen point of vacuum infiltration

d¹ radiologiczn¹ w urz¹dzeniu uCT firmy Scanco Medical.(RYS.1c).

W celu dok³adniejszej kontroli wybrane cylindry przeba-dano metoda mikroskopii skaningowej Mikroskopem FirmyJeol przed i po chemicznym wyplukaniu fazy ceramicznej.

Celem otrzymania jednorodnego materia³u a tym samympo³¹czenia metalicznego pomiêdzy struktur¹ otwarto poro-wat¹ a materia³em litym wykonano formy solne wype³nionewype³niaczem ceramiczny i ukszta³towane aby zgromadziæmateria³ lity schemat numer

W dalszym etapie badañ u¿yto ró¿nego rodzaju kszta³-tek odpowiedni z preparowanych celem usuniêcia warstwytlenku magnezu i przygotowanych w podgrzanej formiewype³nionej ceramicznym wype³niaczem.

Wyniki

W procesie odlewniczym, jak ukazuje RYS.5 wykaza-no, i¿ mo¿liwe jest otrzymanie t¹ metod¹ jednofazowej struk-tury hybrydowej. Mo¿na otrzymaæ struktury o gradientowymroz³o¿eniu porów otwartych. Konieczne s¹ dalsze badaniaw optymalizacji powy¿szej metody celem dostosowania nakonkretne aplikacje.

a) b) c)

RYS.1. a) Ceramiczne wype³nienie formy przedinfiltracj¹ ciek³ym stopem magnezu NaCl, b)Zg³ad: materia³ kompozytowy osnowamagnezowa wype³niona ceramicznymwype³niaczem z NaCl, c) SEM: Materia³ otwartoporowaty po ca³kowitym usuniêciu ceramicznegowype³niacza.FIG.1. a) NaCl ceramic mould filling before liquidmagnesium alloy infiltration, b) Microsection:composite material. magnesium groundmass withNaCl ceramic filling, c) Scanning microscope.Open pore material after complete removal of theceramic filling.

RYS. 2. Kszta³tki ze stopu AZ91 zatopione wtworzywie otwarto porowatym ze stopu AZ 91.FIG. 2. AZ91 shapes founded in open pore AZ91.

RYS. 3. Usytuowanie kszta³tek w formie zwype³niaczem ceramicznym.FIG. 3. Shape location in the mould with ceramicfilling.

RYS. 4. Hybrydowymateria³ kompo-zytowy przed usuniê-ciem wype³niaczaceramicznego.FIG. 4. Hybridcomposite materialbefore ceramic fillingremoval.

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of the mould in the process of simultaneous manufacturingof the hybrid material.

In the mould pouring process for the magnesium shapeswith the same alloy in the mould with ceramic filling, it is acertain difficulty to dispose of the surface layer of magne-sium oxide from the surface of the shapes, despite properpreparation by mechanical removal of the oxide layer

The first problem may be solved by manufacturingenough hermetic mould, which is revealed by further re-search. The problem of oxide layers, in turn, seems to besolved by manufacturing the cast in the protective gas at-mosphere, preparing the magnesium shapes and maintain-ing them in appropriate for the casting process tempera-ture, preventing the oxides from locating on the surface bymelting the surface layer.

Acknowledgements

The authors wish to tank for help and support to theGerman Scientific Collectivity.

W metodzie drugiej dokonywano badañ metod¹ mikro-tomografii komputerowej stanu odlewu stopu magnezu zwype³niaczem ceramicznym, oraz po jego usunieciu che-micznie ze stopu. Jak wykazuj¹ RYS.5 odpowiednio z wy-pe³nieniem i bez, charakterystyka w mikro-CT pozwala nadokladne okrelenie zawartoci wype³niacza ceramiczne-go w g¹bce magnezowej. Brak badañ jakociowych na tymetapie procesu wytwarzania mo¿e okazaæ bezu¿ytecznoæproduktu w czasie badañ czasu resorbcji. Wype³nienie ce-ramiczne NaCl w roztworze H2O prowadzi do lokalnychognisk korozyjnych dyskwalifikujacych omawiany materia³jako wypelnienie ubytkow kostnych.

Dyskusja

Jakoæ wytworzonego materia³u hybrydowego okrelo-no na podstawie stanu po³¹czenia materia³u litego ze struk-tur¹ otwarto porowat¹. Wydaje siê, i¿ najwiêkszy problemwi¹¿e siê w procesie jednoczesnego wytworzenia materia-³u hybrydowego z odpowiednim uszczelnieniem formy iodpowiednio dobranym miejscem infiltracji podcinieniemformy. W procesie odlewniczego zalewania kszta³tek ma-gnezowych tym samym stopem w formie wype³nionej cera-micznym wype³niaczem trudnoci przysparza odpowiedniepozbycie siê warstwy powierzchniowej tlenku magnezu nakszta³tkach mimo odpowiedniego przygotowania poprzezmechaniczne ci¹gniecie warstwy tlenku.

Rozwi¹zaniem kwestii pierwszej wydaje siê wykonanieodpowiednio szczelnej formy, co ukazuj¹ dalsze badania iich wyniki. Natomiast w kwestii pokrywania tlenkiem wyda-je siê, i¿ wykonanie odlewu w atmosferze gazu ochronne-go, przygotowanie kszta³tek magnezowych i utrzymywanieich w odpowiedniej do procesu odlewniczego temperatu-rze, blokuj¹cej mo¿liwoci lokowania siê tlenków magnezupoprzez stapianie warstwy powierzchniowej jest odpowied-nim rozwi¹zaniem, co ukazuje niniejsza praca.

Podziêkowania

Autorzy dziêkuj¹ za pomoc i wsparcie Niemieckiej Wspó-nocie Naukowej.

RYS. 5. Badaniakontroli jakociowejw micro-CT firmyScanco medical.FIG. 5. Qualitycontrol in the ScancoMedical CAµT.

References[4] Bach Fr.-W., Kucharski R., Bormann D.: Proceed. ofXXII Con-ference of Orthopaedics of Polish Armee, Bydgoszcz, 2005.[5] Bach Fr.-W, Bormann D., Kucharski R., Wilk P.: Production nadPropereties of Foamed Magnesium; Cellular Metals and Polymers,Eds. R.F.Springer, C.Korner, V.Altstadt, H.Munstedt,Prans.Tech.Publ., Zurich 2005, pp.77-80.[6] Bach Fr.-W., Bormann D., Kucharski R.: November Colloquium2005.

Pimiennictwo

[1] Switzer EN.: Resorbierbares metallisches Osteosynthesema-terial - Untersuchungen zum Resoptionsverhalten im Meerschwe-inchenmodell, Vet.Met.Diss., Hannover, 2005.[2] Schritt in die Zukunft - Medizintechnik gefordert durch das BMBFBundesministerium fur Bildung und Forschung., Bonnj 2001.[3] Ch³opek J., Bach Fr.-W., Kucharski R., Bormann D.: Nowe im-planty dla chirurgii kostnej z resorbowalnych metali i polimerów,Proceed. of ITEM, Bytów, 2006.

Charakterystyka studium:

Zajęcia obejmujące wykłady i seminaria, dotyczyć będą kluczowych zagadnień z dziedziny inżynierii bio-materiałów. Program studiów obejmować będzie charakterystykę tworzyw wykorzystywanych w medycy-nie: metali i ich stopów, polimerów, ceramiki oraz węgla syntetycznego i kompozytów. Omówione zostaną przykłady zastosowań tworzyw syntetycznych w różnych dziedzinach medycyny a mianowicie ortopedii, chirurgii kostnej, laryngologii, kardiologii, okulistyce i stomatologii i innych. Przedstawione zostaną metody projektowania i wytwarzania materiałów spełniających wymagania stawiane przez medycynę. Słucha-czom studium zaprezentowane zostaną metody fi zykochemiczne stosowane zarówno do charakterystyki materiału jak i przebiegu jego degradacji (w sztucznym i naturalnym środowisku biologicznym) oraz me-tody biologiczne do analizy zjawisk zachodzących na powierzchni tworzyw implantacyjnych w kontakcie z żywą komórką i tkanką. Na zajęciach prezentowane będą (w oparciu o konkretne przykłady) metody: FTIR, SEM, AFM, mikroskopia optyczna oraz badania mechaniczne z uwzględnieniem badań parametrów mechanicznych naturalnych tkanek oraz metody analizy fi zycznych parametrów powierzchni (energia powierzchniowa, twardość, chropowatość). Wykłady dotyczyć będą badania biozgodności w warunkach in vitro i in vivo, omówienia normy ISO 10993 (Biologiczna ocena wyrobów medycznych) oraz regulacji prawnych i aspektów etycznych związanych z badaniami na zwierzętach. Dodatkowo omówione zostaną sposoby organizacji, nadzoru i monitorowania badań klinicznych.Słuchacze studium zapoznani zostaną z najnowszymi osiągnięciami inżynierii tkankowej, metodami wytwarzania podłoży tkankowych i konstrukcją bioreaktorów.


STUDIA PODYPLOMOWE 2006/2007 Nazwa studium podyplomowego:

Biomateriały – Materiały dla Medycyny

Organizator studium podyplomowego:

Akademia Górniczo-Hutnicza

Wydział Inż ynierii Materiałowej i Ceramiki Katedra Biomateriałów

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Czas trwania: Jeden semestr (letni 2006/2007)

Zasady naboru: Zgłoszenie pisemne z deklaracją opłaty za studium.

Termin zgłoszeń: 02.02. 2007

Opłaty: 1.800 PLN

Informacje dodatkowe: Zajęcia – 8 zjazdów 18 godzinnych

Przewidywana ilość godzin -144. przewidywana data rozpoczęcia 24.02. 2007.

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