Hydroxyapatite/TiO₂ composite coatings by micro-arc oxidation and electrophoresis deposition and its biological properties

A layered HA(hydroxyapatite)/TiO₂ composite coaling was deposited on pure titanium using micro-arc oxidation pre-treatment and electrophoresis deposition technique. Surface morphology and formation procedure of the coating at various stages were observed by scanning electron microscope. Element component and phase component of the coating was analyzed by energy dispersive X-ray analysis and X-ray diffraction. The adhesive strength of the coating was tested by shear bonding experiment. In order to investigate the bioactivity and biocompatibility of the coating, the titanium discs with the HA/TiO₂ coating were sterilized and after that, MC-3T3-El osteoblast-like cells were cultured on the surface of the discs. The results indicate that the coating consists of the dense TiO₂ interlayer, the intermediate layer of a composite of the HA/TiO₂ coating and the top pure HA layer. The average adhesive strength of the coating is (19.3+2.5) MPa. The observation of immunofluorescence coloration indicates that osteoblast-like cells can build good adhesion to the coating and spread well after cultured for 3 h. The amount of cells attached to the coating increases with the increase of time. So it shows that the HA/TiO₂ coating deposited by micro-arc oxidation and electrophoresis deposition technique has good bioactivity and biocompatibility, and it possesses a very good combination of biochemical stability and mechanical properties.