engleski

Biomimetic Design of New Organic/Inorganic Nano-composite Coatings for Artificial Implants

Osteointegration of artificial implants for bone and tooth replacement or repair is facilitated by coating the surfaces of bioinert hard materials (metals, polymers) with calcium phosphate containing coatings. We prepared a new class of organic-inorganic nano-composite coatings by a two-step procedure: (i) embedding several layers of amorphous calcium phosphate (ACP) particles between organic polyelectrolyte multilayers, obtained by alternate deposition of poly-L-lysine (PLL) and poly-L-glutamic acid (PGA). (ii) When organic – inorganic coatings of the required thickness were obtained, the material was immersed into a metastable calcifying solution to initiate “ in situ” crystal growth of nano-crystalline apatite within the organic matrix. With calcium phosphate as the top layer, SEM, EDS and thin layer X-ray diffraction revealed micron size octacalcium phosphate crystals, OCP, growing perpendicularly to the substrate surface. Such crystals anchored the coatings to the metal surface but were not conducive to cell attachment. However, coatings containing final PLL-PGA-layers were true nanocomposites with smooth surfaces containing nanocrystalline apatite, as shown by thin layer XRD. Mechanical and biological tests showed that such coatings possess appropriate biomechanical stability with well adapted sites for cell adhesion and proliferation. Moreover, after two months of implantation into the hind legs of rabbits, bone bonding onto coated samples was two times stronger than onto chemically etched bare titanium plates. The good correlation of in-vitro and in-vivo tests clearly indicates that the organic-inorganic nanocomposite is a very promising surface coating with wide medical applications. Acknowledgement: The financial support by the European Commision (Fifth framework, contract # GRD-2000-00423) is gratefully acknowledged.

organic-inorganic composites

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