Biomimetic Electrodeposition of Hydroxyapatite onto TiO2 Nanotubes Modified by L-Aspartic Acid

Bond strength of the hydroxyapatite (HAP) coating on the implant material is very critical as it has to withstand crevice and bone growth stressing in implant applications. In this paper, we have reported a novel biomimetic method to improve the bond strength by electrodeposition of hydroxyapatite on the TiO₂ nanotubes modified by L-aspartic acid (L-Asp). An array of vertically aligned titanium oxide nanotubes was grown on the surface of titanium substrate by anodization. The electrophoresis in L-aspartic acid solution causes the adherence of L-aspartic acid to the wall of TiO₂ nanotubes from the bottom to the brim which chelates Ca^{2 *} as the center of nucleation to induce the deposition of the hydroxyapatite within and in-between the nanotubes. After the subsequent electrodeposition of hydroxyapatite nanocrystalling coating, the nanopores within and in-between TiO₂ nanotubes were filled with the hydroxyapatite crystals. As a result, the bond strength between the HAP coating and titanium substrate was dramatically improved.