Photocatalytic Deposition of Hydroxyapatite onto a Titanium Dioxide Nanotubular Layer with Fine Tuning of Layer Nanoarchitecture

A new effective method of photocatalytic deposition of hydroxyapatite (HA) onto semiconductor substrates is proposed. A highly ordered nanotubular TiO2 (TNT) layer formed on titanium via its anodization is chosen as the photoactive substrate. The method is based on photodecomposition of the phosphate anion precursor, triethylphosphate (TEP), on the semiconductor surface with the following reaction of formed phosphate anions with calcium cations presented in the solution. HA can be deposited only on irradiated areas, providing the possibility of photoresist-free HA patterning. It is shown that HA deposition can be controlled via pH, light intensity, and duration of the process. Energy-dispersive X-ray spectroscopy profile analysis and glow discharge optical emission spectroscopy of HA-modified TNT prove that HA deposits over the entire TNT depth. High biocompatibility of the surfaces is proven by protein adsorption and pre-osteoblast cell growth.