The characteristics of in vitro biological activity of titanium surfaces anodically oxidized in chloride solutions

Photo-functionalized radical reactions on TiO2 have been correlated with adsorption of organic impurities and decreasing hydrophilicity of titanium-based biomaterials. Such reactive oxygen species (ROS) spontaneously generated on oxidized titanium surfaces may also have important roles against time-dependent degradation of biological ability and adherent micro-organisms. This study examined in vitro biological ability as a function of time and antimicrobial activity on oxidized titanium surfaces without photo-functionalization. Mechanically polished titanium and thermally oxidized titanium surfaces that had been stored for 4 wks showed adsorbed organic impurities with decreased surface hydrophilicity. Even after the storage period, anodically oxidized titanium surfaces enabled super-hydrophilicity without adsorption of organic impurities, because of the ROS and the hydrophilic functional groups generated on the surfaces. The osteogenic gene expressions of osteoblasts cultured on anodically oxidized titanium surfaces with or without storage were significantly higher than those on thermally oxidized titanium and polished titanium surfaces. Titanium surfaces anodically oxidized in a solution with chloride achieved antimicrobial activity against an oral microorganism due to the amount of ROS generated on the surface. Thus, titanium anodically oxidized in solution with chloride may have potential use for titanium-based internal fixation devices.