A study on the mechanism of protein adsorption to TiO2.

The hypothesis that calcium ions adsorb to TiO2 and further to macromolecules with high affinity for Ca2+ was tested. The reaction of human serum proteins with TiO2 was examined and compared with the reaction with hydroxyapatite. The oxide covered titanium surfaces reacted with calcium when exposed to CaCl2 and calcium was identified to a depth of 17 nm into the oxide layer. Surface adsorbed serum proteins were dissolved by EDTA and analysis by the SDS-PAGE technique revealed that the surfaces of TiO2 and hydroxyapatite appeared to take up the same proteins selectively from human serum. Albumin, prealbumin and IgG were identified by immunoelectrophoresis. It is suggested that calcium binding may be one mechanism by which proteins adsorb to TiO2. It is well established that this is the case with hydroxyapatite.