Hydroxyapatite growth on anodic TiO2 nanotubes

In the present work, we study the growth of hydroxyapatite formation on different TiO2 nanotube layers. The nanotube layers were fabricated by electrochemical an-odization of titanium in fluoride-containing electrolytes. To study various nanotube lengths, layers with an individual tube diameter of 100 nm were grown to a thickness of approximately 2 mu m or 500 nm. The ability to form apatite on the nanotube layers was examined by immersion tests combined with SEM, XRD and FT-IR investigations. For reference, experiments were also carried out on compact anodic TiO2 layers. The results clearly show that the presence of the nanotubes on a titanium surface enhances the apatite formation and that the 2-mu m thick nanotube layer triggers deposition faster than the thinner layers. Tubes annealed to anatase, or a mixture of anatase and rutile are clearly more efficient in promoting apatite formation than the tubes in their "as-formed" amorphous state. (c) 2006 Wiley Periodicals, Inc,