Advances in Biomaterials II




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НазваниеAdvances in Biomaterials II
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SBPMat

BRAZIL-MRS


2nd Brazilian MRS Meeting

October 26-29, 2003


Symposium B:


Advances in Biomaterials II


Symposium Organizers:____________________________________________________




José Carlos Bressiani (IPEN)


Carlos Frederico de Oliveira Graeff (USP-Ribeirão Preto)


Marcos Farina (UFRJ)





iNVITED PRESENTATIONS







B-I1

ROUGH SURFACES OF TITANIUM AND TITANIUM ALLOYS FOR IMPLANTS AND PROSTHESES

1E. Conforto, 2B.-O.Aronsson, 3A. Salito, and 4D. Caillard; 1Swiss Federal Institute of Technology (EPFL), CH-1015, Lausanne, Switzerland; 2GAP Biomedical, University of Geneva, CH-1211 Geneva 4, Switzerland; 3Sulzer-Metco AG, CH-5610 Wohlen, Switzerland; 4CEMES/CNRS, 29 rue Jeanne Marvig, F-31055 Toulouse Cedex 4, France.


Titanium and titanium alloys for dental implants and hip prostheses were surface-treated and/or covered by metallic or ceramic rough layers. The goal of these treatments is to improve the surface roughness and, consequently, the osteointegration, the fixation and the stability of the implant. Their microstructure has been studied and correlated to their mechanical behavior. As-treated and mechanically-tested surfaces were characterized by scanning electron microscopy (SEM). Structural analyses performed by transmission electron microscopy (TEM), mainly in cross-section, reveal the degree of adherence and cohesion between the surface layer and the substrate (implant). Phase transformations at the surface, intermediate crystallographic phases formed between the surface layer and the substrate, and crystallographic relationships between them were also identified and analyzed by this technique. Moreover, dislocation analyses by TEM allowed us evaluating the degree of plastic deformation in the surface layer and at its interface with the substrate.



B-I2

NEW MATERIALS FROM NATURAL RUBBER

Leonardo F. Valadares, Márcia M. Rippel and Fernando Galembeck, Institute of Chemistry, Universidade Estadual de Campinas, Campinas SP, Brazil.


Natural rubber latex has some outstanding properties responsible for its unmatched role in some industrial products, as for instance the auto tires, adhesives and surgical gloves. However, these properties are often dependent on chain crosslinking procedures that do also make the rubber resistant to biodegradation thus creating well-known problems such as that of tire disposal, for example. In this laboratory, we have explored two new alternatives for making natural rubber materials but without using covalent rubber chain crosslinking: nanocomposite formation and ionic crosslinking. Rubber latex is an ideal raw material for making a clay nanocomposite because this requires clay exfoliation and the latex aqueous serum is an excellent clay exfoliating agent. Montmorillonite-natural rubber composites were prepared by admixture of clay and rubber latex, under temperature and mixing conditions. The products are translucent and strongly birefringent, evidencing that the clay is largely exfoliated and oriented within the rubber as confirmed also by X-Ray diffraction and electron microscopy. Evidence for ionic crosslinking was obtained from solubility, microscopy and dye sorption experiments. This is now the basis for a new approach for natural rubber as well as other polymer latex modification.



B-I3

OSTEOBLAST ATTACHMENT AND ADHESION: THEY ARE REALLY NOT TWO OF KIND

F.C. Silva Filho1*, G.C.Menezes1, A. Tempone2, and C.N.Elias3. 1UFRJ-Instituto de Biofísica Carlos Chagas Filho, 2FIOCRUZ- Instituto Oswaldo Cruz, and 3UFF-Escola de Engenharia Industrial e Metalúrgica, Volta Redonda, Rio de Janeiro, Brazil.


Most of cells need to be bound to surfaces in order to survive and proliferate, a requirement that has been named anchorage dependence. The simplest interpretation of this phenomenon might be that cell behavior is controlled by biochemical signals generated by specific surface receptors, particularly integrins, when they meet their ligands. However, data accumulated in the literature have been clearly indicating that this is not the whole story. Geometrical parameters of a surface may also affect the activation of cell function, including gene activation. The main job of a bone tissue engineering is, therefore and at first glance, to provide a surface where osteoblasts might attach leading to gene activation concerning adhesion and differentiation. We have assayed different types of surfaces (engineered titanium and slides made of glass or polystyrene) coated or not with human plasma fibronectin to study osteoblast attachment and adhesion. Each one of these osteoblast properties were here monitored looking for the expression of PHEX (phosphate-regulating gene homologies to endopeptidases on the X-chromosome) by using cDNA technology and reactivity to the Mab OB7.3.



B-I4

CHITOSAN AND COMPOSIT FILMS. CHARACTERIZATION, APPLICATIONS, BACTERICIDES STUDIES FOR BURNING TISSUES AND CELL GROWING

Galo Cárdenas.1, Lucia Cruzat1 , Carlos Rojas2, S. Patricia Miranda3 and Andres Gutierrez4. 1Depto Polímeros, Fac. Ciencias Químicas, Univ. de Concepción, Concepción, Chile. gcardena@udec.cl 2Hospital Naval, Talcahuano Base Naval, Chile. 3Fac. Estudios Superiores Cuautitlán, Cuautitlán Izcalli, UNAM, México. 4Centro Nacional Rehabilitación, México DF 14389.


In most of the patients with burns over 40% corporal surface, the skin reconstruction must be carried out with skin graft at a deep containing dermis and epidermis from the healthy skin of the patient. However, the risk for infection, in the donant zone is damaged with scar and pigmentation changes which depend on the dermis thickness extracted in the graft. The chitosan is an excellent candidate for treatment of damaged areas produced by burns either from fire, chemical, hot water and ulcer injuries. The mechanism is explain as follows: the chitosan can produce films or biocompatible films and adsorbents. Their application can be done using a film previously prepared or a liquid solution placed directly over the damaged area producing a film “in situ”. These film shows permeability to oxygen with antagonism on the hypoxia of damage tissues and their weak acidity produces a fresh anaesthesic effect. Their degradation by enzymes allows to avoid the removal. Our goal has been the use of several chitosan MW ranges: 60.000, 100.000 and 250.000 g/mol with a high DA as a source to prepare chitosan films. A full characterization by FTIR, TGA and SEM was carried out. The bactericide properties of the films and composite against positive and negative gram bacterias was carried out.



B-I5

BIOMATERIALS MANUFACTURING THROUGH BIOMIMETICS

J.L. Arias and M.S. Fernandez, Faculty of Veterinary Sciences and Center for Advanced Interdisciplinary Research in Materiasls, Universidad de Chile, Santiago, Chile


Modern times need innovative technological approaches for controlled fabrication of crystalline materials with complex forms and novel properties. For building their hard tissues, living organisms have develop a large variety of procedures leading to the formation of precisely controlled inorganic-organic composites, in which the minute organic component exerts significant control on the mineralization process. This results in the formation of structures with uniform-sized particles, novel crystal morphologies, specific crystallographic orientation and interesting properties. These biological procedures have inspired a large class of biomimetic advanced materials, especially organic/inorganic composites. Through the study of egg- and seashell formation it has been possible to learn about how biology builds crystalline materials. While traditional engineering processes use “top-down fabrication techniques”, biology uses a “bottom-up approach”. That means biological hard tissues are fabricated by a molecular self-assembly process of building blocks, one atom or molecules at a time. Such strategy involves a spatio-temporal production and deposition of inert organic substrates, soluble charged macromolecules orienting crystal nucleation and growth, and other macromolecules finishing the process.



B-I6

CHARACTERIZATION AND PROPERTIES OF NANOSTRUCTURED CALCIUM PHOSPHATES

A.M. Rossi and J. Terra, CBPF, 22290-180, RJ, Brazil, G.A. Soares, COPPE/UFRJ, P.O. Box 68505, RJ, Brazil; M. Farina, ICB/UFRJ, RJ, Brazil, R. Borojevic, ICB/UFRJ, 21941-590, RJ, Brazil, D. E. Ellis, Northwestern University, Evanston, Il. 60208, USA.


Calcium phosphates and specially hydroxyapatite, HA, are some of the most important bioceramics for bone reconstruction. In the last years great efforts have been made to improve HA mechanical properties and bioactivity. Changes in the HA surface, combination with inorganic and organic compounds and molecule adsorption have been proposed. In some of these studies composites containing HA and organic molecules have been precipitated in experimental conditions in which the HA crystals achieved dimensions close to those of bone apatite. The resulting nanocomposites had mechanical properties and bioactivity similar to bone. In this presentation we will show that the decrease in crystal size induces important modification on HA chemical and structural properties such as surface activity, crystallinity, dissolution rate, molding and sintering behavior. We will discuss how organic molecules or metal impurities inhibit hydroxyapatite nucleation and decrease its crystal dimensions. It will be shown that even pure HA can be precipitated with crystal dimensions smaller than 10 nm, which correspond to a HA with total surface area higher than 200 m2/g. The potential of nanostructured calcium phosphate for use as bone graft material is then discussed.



B-I7

INFLUENCE OF BIOMATERIALS ON THE STRUCTURE OF CELL ADHESIONS

J.G.B. Nebe1, F. Luethen1, A. Diener1, R. Lange2, P. Becker3, J. Rychly1

1Department of Internal Medicine and 2Department of Electrical Engineering, University of Rostock, Ernst-Heydemann-Str. 6, 18057 Rostock, Germany, 3DOT Ltd., Charles Darwin-Ring 1a, 18059 Rostock, Germany.


To promote tissue formation after implantation, the biomaterial should provide a highly biocompatible substrate to enable cell adhesion, migration, proliferation, and differentiated function. Biocompatibility studies therefore are increasingly focussed on very sensitive parameters to examine molecular mechanisms, e.g. of cell adhesion components. In our investigations both on modified titanium, and on the biodegradable poly--hydroxy butyric acid (PHB), the cell adhesions were structurally influenced compared to cells grown on collagen: In osteoblastic cells the formation of integrin adhesions and of the cytoskeletally anchored protein vinculin was changed. We observed differences in the organization and alignment of the actin cytoskeleton and of extracellular matrix proteins. Furthermore we revealed dynamic changes of GFP-vinculin and GFP-actin due to the titanium material. In epithelial cells on PHB we found alterations of cell spreading and in the distribution of tight junction proteins. Because the organization of adhesion mediated components are related to the cell physiology biomaterial characteristics should maintain these cellular structures.



B-I8

BIOCOMPATIBILITY AND OSSEOINTEGRATION OF BONE IMPLANTS

B. König Jr., Department of Anatomy, ICB, University of Sao Paulo, Av. Lineu Prestes, 2415, 05508-900, SP, Brazil. L. J. Faria Jr, CEDDA Av. São João, 89, 12220, S.J. Campos, SP, Brazil. M. J. Carbonari, IPEN, P. O. Box 11049, Pinheiros, 05422-970, SP, Brazil.


The calcification of the bone tissue process is already well known and it is classic in our knowledge that there are two main processes, the intramembranous and the endochondral one, already described in different scientific levels with a variable amount in quantity as well as in quality. Nowadays we know that there is no essential difference between the two kinds of ossification. The principles of osteoconduction are better known and controlled in researches with implant. In our researches we made biocompatibility and osseointegration evaluations with different materials in rabbits. Different fluorescent markers were inoculated in rabbits to show the periodic deposition of bone around the implants and show the period of bone deposition and reorganization. Novel non-toxic bioactive phosphate glasses were developed. The presence of these glasses stimulated the bone growth in the medullar region. Methods for critical analysis were employed in order to observe different aspects of the biocompatibility. The distance in relation to the compact bone was taken in to account. Mathematics equations and graphics ware developed to allow a scientific approach to the problem.



B-I9

BIOMIMETIC APATITE FORMATION ON PRETREATED BIOINERT MATERIAL SURFACES

F.A.Mueller, L.Jonasova, P.Greil, University of Erlangen-Nuernberg, Department of Materials Science, Martensstr. 5, 91058 Erlangen, Germany.


Bioinert materials are generally encapsulated by fibrous tissue after implantation into the living body. It is known that a limited number of bioactive ceramics can bond to living bone without formation of fibrous tissue. These materials create an apatite layer on their surface after implantation. In our studies we investigated the in vitro growth of bone-like apatite layers in physiological environment on titanium and cellulose implant surfaces, respectively. The implant material surface was modified by a chemical pretreatment with hydroxide solutions containing alkaline or earth alkaline metals, or by coating the surface with a bioactive gel. Exposure of the pretreated implants to simulated body fluid (SBF) stimulates rapid in vitro formation of a bone-like hydroxy carbonated apatite (HCA) layer. Nucleation of HCA was found to be influenced by ion exchange reactions in a hydroxide gel layer which initially formed on the implant surface. Biomimetically grown HCA-layers are of particular interest for the generation of bioactive interfaces between load bearing protheses and the surrounding tissue matrix as well as functional scaffold structures for tissue engineering. Low processing temperatures (37°C) offer the possibility to incorporate functional bioorganics like morphogenic proteins or cytokines in an inorganic/organic hybrid HCA-layer.



B-I10

PREPARATION OF CALCIUM CARBONATE LAYERS FOR THE COATING OF METALLIC AND NON-METALLIC PROSTHESIS

Jean Pierre Manaud; Yann LE PETITCORPS* ICMCB-CNRS-UPR 904887, Av. A Schweitzer 33608 Pessac France lepetit@icmcb.u-bordeaux .fr


Calcium carbonate layers were deposited on titanium and carbon/carbon composites by reactive plasma assisted evaporation (RPAE). Cylinders of coral (Porites Lutea) were first decomposed to a calcium monoxide and then used as a source for the evaporation. A plasma gas containing a large amount of CO2 was used to promote the reaction with the evaporated material and to get the deposit. By adjusting the experimental parameters, a coating rich in calcium carbonate (80 mol.%CaCO3 and 20 mol.% CaO) can be obtained at a relatively high rate of deposition (200 nm/min). Non-destructive infra red spectroscopy and destructive thermogravimetry analysis were done to determine the qualitative and quantitative composition of the coating.



B-I11

THE BIOMATERIALS PROGRESS: A GENERAL VIEW

A. C. Guastaldi Grupo de Biomateriais, Instituto de Química da UNESP, Rua Prof. Francisco Degni, S/N, Araraquara, São Paulo, Brazil; Caixa Postal 355, 14801-970, Araraquara, SP, Brazil, guastald@iq.unesp.br


In this conference It will be presented a general view about the biomaterials progress. The biomaterials science is an interdisciplinary field that represent one of the more and sophisticated trends in the worldwide medical practice. This lecture will give us a general idea about the titanium and some others inorganic materials used as biomaterials. Commercially pure cpTi, titanium alloys, hydroxyapatite-Ca10(PO4)6(OH)2 coated and Al2O3 are considered very important in the dental and orthopaedic applications because of its excellent biocompatibility and proper mechanical properties, but more recently apatites coating by sol-gel and biomimetic routes is commom practice in order to improve the biocompatibility, bioactivity and the corrosion resistence of metallic implants. It will be approach also the interactions among the several scientific and technologic areas present in the biomaterials development and clinical applications.


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