Mechanism of adsorption of human albumin to titanium in vitro.

Our previous studies have shown that human albumin is one of the main salivary proteins that adsorb to titanium (Ti). The goal of the present study was to investigate the role of electrostatic interactions in the adsorption of human albumin to Ti-oxide (TiO2) in vitro. The binding profile of human albumin to Ti was analyzed according to an adsorption isotherm. Purified human serum albumin (HSA) was suspended with native, calcium-, magnesium-, or potassium-treated commercially pure Ti powders, at pH 3.0 and 7.0. The amount of unadsorbed protein in the supernatant fluid was measured. The maximum amount of adsorbed albumin was 0.13 mg/1.0 g Ti. The albumin-Ti association constant was 2.77 mL/mg. Pretreatment of Ti with calcium, or magnesium alone, or combined with increasing pH values (3.0-7.0) resulted in augmented adsorption of HSA to Ti. No increase in adsorption was observed following pretreatment of Ti with potassium. These results point to the involvement of electrostatic interactions in the adsorption of HSA to TiO2.