Effect of surface hydroxyl groups and surface energy of titanium on adsorption of bovine serum albumin

Bioactivity of titanium depends on the characteristics of its surface oxide film. This paper focuses on the relationship between the adsorption of bovine serum albumin and both important characteristics, i.e., surface energy and surface hydroxyl groups. The surface oxide films on titanium were fabricated by heat-treatment in different oxidation atmospheres, such as air and water vapor. Surface energies were calculated from contact angles of several liquids on titanium surfaces. Percentages of surface hydroxyl groups were obtained by X-ray photoelectron spectroscopy analysis. Heat-treatment increased both the surface energy and the amount of surface hydroxyl groups on titanium. The different oxidation atmospheres resulted in different percentages of oxygen species in TiO2, in physisorbed water and acidic hydroxyl groups, and in basic hydroxyl groups on the titanium surfaces. The adsorption of bovine serum albumin on the titanium surfaces was positively related to the amounts of the surface hydroxyl groups including basic hydroxyl groups and acidic hydroxyl groups, and the values of the polar component of the total surface energy. The bovine serum albumin chemically adsorbed onto the titanium surfaces.