Biomimetic apatite coatings on micro-arc oxidized titania.

Biomimetic apatite coatings on micro-arc oxidized titania films were investigated and their apatite-inducing ability was evaluated in a simulated body fluid (1.0 SBF) as well as in a 1.5 times concentrated SBF (1.5 SBF). Titania-based films on titanium were prepared by micro-arc oxidation at various applied voltages (250-500 V) in an electrolytic solution containing beta-glycerophosphate disodium salt pentahydrate (beta-GP) and calcium acetate monohydrate (CA). Macro-porous, Ca- and P-containing titania-based films were formed on the titanium substrates. The phase, Ca and P content, morphology, and thickness of the films were strongly dependent on the applied voltage. In particular, Ca- and P-containing compounds such as CaTiO3, beta-Ca2P2O7 and alpha-Ca3(PO4)2 were produced at higher voltages (>450 V). When immersed in 1.0 SBF, a carbonated hydroxyapatite was induced on the surfaces of the films oxidized at higher voltages (>450 V) after 28 days, which is closely related to the Ca- and P-containing phases. The use of 1.5 SBF shortened the apatite induction time and apatite formation was confirmed even on the surface of the films oxidized at 350 V, which suggests that the incorporated Ca and P in the titania films play a similar role to the Ca- and P-containing compounds in the SBF.