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Campus des Cézeaux
24, avenue des Landais
BP 80026
63177 Aubière Cedex
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Accueil du site > Recherche pluridisciplinaire > Biomatériaux > Research activities
Research activities
Our research activities are muti-disciplinary :
- (1) to take part, in collaboration with industrials, chemists and biologists to the development of bioactive biomaterials used as osseous substitutes or as prosthetic coatings ;
- (2) to study the influence of the surface morphology and the composition of these materials on their properties of integration, of bioactivity and of dissolution ;
- (3) to characterize at the micrometer and at the nanometer scale by ions and electron beams interfaces between these materials and bone tissues ;
- (4) to optimize these methods in order to perform quantitative measurements and to analyse diffusible ions.
BIOACTIVE CERAMICS
A bioactive material generates a series of physicochemical reactions (dissolution, precipitation) occurring at implant/host tissues interface. These reactions can lead to the formation of a calcium phosphate (apatite) layer which permits a strong chemical interfacial bond. This type of fixation is called ‘bioactive fixation’.
- Bioactive Glasses
One of our objectives relates to the development of bioactive glasses to controlled dissolution and bioactivity properties, adapted to specific clinical applications (osseous substitutes, prosthetic coatings). The kinetics and the amplitudes of these processes can be modulated by the presence and the concentration of certain elements and by the material structure. We study glasses prepared by sol-gel method
- Elaboration of bioactive and nanostructured glasses by Sol-Gel method
In collaboration with the LMI (Clermont-Ferrand), we work on the elaboration of bioactive glasses in binary (SiO2-CaO) and ternary (SiO2-CaO-P2O5) systems.
This method permits to control the glass structure at the nanometer scale. The glass is obtained at low temperatures and the control of synthesis parameters (solvant, catalysis, ratio water/alkoxides,…) and conditions of temperature treatment permit to modulate the materials texture (porosity, size of pores, specific surface,…). Moreover, uses of molecular precursors (salts or metallic alkoxides) in solution which lead by a process of hydrolyse/condensation to the formation of a gel, permits to give an excellent purity to the final product and to modify the material composition. This work will lead to a specific control of bioactive properties of the bioactive glasses.
- Calcium Phosphates
Phosphocalcic ceramics presents interesting properties to fill osseous defects and for the coating of metallic prostheses in orthopaedic and dental surgery. Calcium phosphate ceramics are biocompatible and are predisposed to be colonized by living tissues, this thanks to the presence of macro-pores ( » 300 µm). With a chemical composition and a crystallographic structure of the apatite crystals close to those of calcified tissues, hydroxyapatite Ca10(PO4)6(OH)2 is a very interesting biomaterial. On the other hand, this synthetic material is predisposed to accept a doping in metal ions. Certain trace elements may have effects on the formation and the stability of synthetic apatites. Moreover, the presence of these elements within the implant can generate a series of physicochemical reactions at the interface with host tissues leading to an intimate bond between the material and bone.
Our previous works concerned pure hydroxyapatite, hydroxyapatite doped with manganese or zinc and biphasic ceramics composed with 25 % of tri-calcium phosphate b (Ca3(PO4)2) and 75 % of hydroxyapatite (Collaboration with Depuy-Bioland company, Toulouse). The results highlighted a faster resorption for hydroxyapatite doped with zinc and biphasic ceramics. These differences can be explained by the fact that tri-calcium phosphate b dissolves and reabsorbs more quickly than pure hydroxyapatite. Concerning zinc, it seems to play a primordial role during resorption process. The determination by XANES of the zinc position within the hydroxyapatite structure could permit to better understand these differences.
- Elaboration of doped and nanostructured hydroxyapatites by Sol-Gel method
In collaboration with the LMI (Clermont-Ferrand), we work on the elaboration of hydroxyapatite doped with zinc (Ca10-xZnx(PO4)6(OH)2) and in strontium (Ca10-xSrx(PO4)6(OH)2) by Sol-Gel method.
This method permits to control the bioceramic structure at the nanometer scale and to dope the materials with ions. This work will lead to a specific control of bioactive properties of the calcium phosphate ceramic.
- Study of bioactive ceramics/biological fluids/cells interactions at the micrometer and nanometer scale
To study bioactive ceramics/biological fluids/cells interactions, we characterize materials/living tissues interface by micro ions beam (PIXE, RBS, STIM) and electrons beam (STEM-EDXS). Ion beam analysis is based on ion-matter interaction and permit to obtain quantitative elemental maps by X-ray emission (PIXE) and density micrograph by energy loss of transmitted ions in the samples (STIM).These techniques give the distribution of major, minor and trace elements at the interface (chemical maps) and micrograph of the biomaterials or living tissues. These measurements show physico-chemical reactions (dissolution, precipitation, ionic release…) occurring at the interface and biological behaviour of tissues in contact with the material.
METAL ALLOYS
Metals and the alloys are very much used for the design of prostheses (Ti6Al4V, Co-Cr …). They have good mechanical and biocompatibility properties. However, there are many problems due to the corrosion of the implants, to the release of metallic debris which lead to reactions of rejection. Thus, the interfacial reactions influence the long-term behaviour of an implant. In order to determine oseointegration of this type of biomaterial, it is necessary to study biological and physicochemical reactions at the bone/implant interface.
In collaboration with the orthopaedic surgeons (CHU of Clermont-Ferrand), we study the processes of elemental migrations, starting from the implanted prosthesis towards surrounding tissues. The goal of this work is to define the role of these migrations on stability in the course of time of the prostheses, and to evaluate their role in certain therapeutic failures (metallosis).
Characterization by PIXE of tissues permits to determine their composition in metal elements (Ti, Al, V, Co, Cr, Ni). Moreover, STEM-EDXS analysis gives information on the morphology, the size, the composition of wear debris and the type of ions released during corrosion of the implant.
PERCOLATION
Currently, we develop a new research topic in collaboration with the team of Theoretical Physics. We try to find a framework theoretical with our experimental results. We simulate resorption of coral and hydroxyapatite implants with the percolation theory.
