Time-dependent growth of biomimetic apatite on anodic TiO2 nanotubes

We report on the initial and later stages of apatite formation from simulated body fluid oil titania with different surface morphologies (Compact or nanotubular) and different crystal Structures (anatase or amorphous). The nanotubular layers were fabricated by electrochemical anodization in fluoride-containing electrolytes. The Study investigates the enhanced apatite deposition on titania nanotubes. In the initial stages of apatite growth, more nuclei are formed oil the nanotubular surface than oil flat compact TiO2. While the crystallographic structure of the Substrate plays a less important role than the morphology in the initial nucleation stages. it is of great importance in the later stages of apatite crystal growth. The nanotubular morphology combined with an anatase Structure leads to the formation of apatite layers with a thickness of > 6 nm in less than 2 days. No stable apatite layers can be observed on amorphous TiO2 films, neither on compact nor oil nanotubular substrates. XPS. FT-IR and XRD measurements reveal that carbonated hydroxyapatite (CHA) of low crystallinity is formed oil annealed nanotubular and compact titania. Electrochemically grown and annealed TiO2 nanotube arrays having anatase Structure are expected to be a good precursor system for the formation of CHA and thus for the preparation of osseointegrative implants. (c) 2008 Elsevier Ltd. All rights reserved.