Formation of hydroxylapatite on CVD deposited titania layers

Bioactive coatings on medical implants can be prepared from titanium dioxide due to its ability to induce the formation of hydroxylapatite (HA) from physiological solutions. In this study TiO2 layers were formed by chemical vapor deposition at different substrate temperatures in order to controllably change their structure from amorphous to consisting of preferentially oriented anatase crystallites. To evaluate the influence of phase composition and surface morphology of the deposited layers on their ability to form HA titania samples were immersed in Dulbecco's phosphate-buffered saline (DPBS). The obtained results showed that structure of TiO2 layers determines the structure of HA formed on their surface. Polycrystalline titania layers with random orientation of anatase crystallites are the most favorable for intensive nucleation and formation of continuous HA coatings in DPBS solution. The textured TiO2 layers with smooth surface enhanced formation of HA deposits which consisted of sparsely distributed large separate grains. On the basis of the experimental results it was proposed that formation of hydroxylapatite nuclei on the surface of titania layers occurs by a mechanism of epitaxial growth. (C) 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim