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Organic-inorganic nanocomposite coatings for enhancement of bioactivity of metal implants

Introduction Metal implants are used for the repair or replacement of teeth and bones with large defects caused by trauma or disease (cancer, osteoarthritis etc). Titanium and its alloys are valued for their excellent mechanical properties, but their bioactivity needs improvement [1]. Our approach is to coat implant surfaces with organic-inorganic nano-composites. The design of the coatings is biomimetic, based on the observation that in biomineralization cells first deposit an organic matrix, then grow calcium phosphate (CaP) crystals upon/within this matrix [2]. Materials and Methods: The organic matrix was deposited on glass or titanium plates as polyelectrolyte multilayers, PMLs, by alternate adsorption of positively and negatively charged polyelectrolyte(s). CaP was nucleated either by co-adsorbed amorphous calcium phosphate (ACP) layers [3] or by functional groups from the organic matrix. Crystals were grown “in situ” by immersing the coated substrate into a metastable calcifying solution (MCS). Bioactivity was assessed by seeding osteoblast-like cells (MC3T3-E1 or SAOS-2) onto the coated surfaces, incubating and determining cell adhesion, proliferation, morphology and cell activity [4]. Results The type and morphology of CaP deposits depended on the type of the crystallization initiator and/or on the composition of the MCS. Crystallization initiated by ACP resulted in spherulitic aggregates of micron-sized OCP crystals (Fig. 1A), whereas direct nucleation on the PEML yielded well spread, nanometer sized crystals of calcium deficient apatite (Fig.1B). Cell proliferation on the coatings was improved by adding a final PEML [3, 4].

nanocomposites; coating; implant

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