Surface Treatments of Titanium Anodized in Phosphoric Acid Solution and in Vitro Cell Responses

Abstract

TiO₂ layer was fabricated on commercially pure titanium using an anodic spark oxidation technique with 1M phosphoric acid solution. Subsequent heat or water treatment was performed to improve the biocompatibility of oxide layers. Surface characteristics of oxide layers before and after subsequent treatments and their influence on the cell response were investigated. It was found that the oxide layer without subsequent treatments exhibited a porous surface structure with few nanometer features. Thin film X-ray diffraction analysis and electron probe microanalysis indicated that the oxide layer consisted of amorphous or poorly crystallized oxides with the incorporation of phosphorus. After heat treatment (500°C, 3 h), the crystallinity degree of oxide layer increased, but only slight change in the surface morphology was observed. In contrast, water treatment (80°C, 48 h) not only can significantly transform the amorphous oxides into crystalline anatase, but also result in a nanostructured surface. In vitro biocompatibility study of oxide layers demonstrated better cell response to water treated oxide layer than untreated one.