Nanocomposite hydroxyapatite formation on a Ti-13Nb-13Zr alloy exposed in a MEM cell culture medium and the effect of H2O2 addition

Titanium alloys are known to nucleate an apatite layer when in contact with simulated body fluid. This improves the bioactivity of titanium implants and accelerates osseointegration. Promoting the formation of hydroxyapatite on biocompatible metals is, therefore, a very important topic of biomaterials research. In this paper, the formation of hydroxyapatite (HA) on the near-beta Ti-13Nb-13Zr alloy by immersion in minimal essential medium (MEM), with and without H2O2 addition, has been studied using electrochemicals methods, scanning electron microscopy and X-ray photoelectron spectroscopy. The in vitro biocompatibility of this alloy was evaluated by cytotoxicity tests. The Ti-13Nb-13Zr alloy exhibits passive behaviour over a wide potential range in MEM and the passive film is composed of an inner barrier layer and an outer porous layer. The addition of H2O2 leads to a thickening of the outer porous layer and strongly reduced cur-rent density. With regard to the surface composition, immersion in MEM solution results in the formation of an island-like distribution of HA + amino acids. Addition of H2O2 to the MEM solution strongly promotes the formation of a thicker, continuous but porous nanocomposite layer of HA + amino acids. The Ti-13Nb-13Zr alloy is non-toxic and the nanocomposite HA + amino acid layer formed in the MEM solution favours the growth of osteoblast cells. For Ti alloys, the release of H2O2 in the anti-inflammatory response appears to be an important beneficial process as it accelerates osseointegration. (C) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.