Mechanistic Study of Protein Adsorption on Mesoporous TiO₂ in Aqueous Buffer Solutions

Protein adsorption is of fundamental importance for bioseparation engineering applications. In this work, a series of mesoporous TiO₂ with various geometric structures and different aqueous buffer solutions were prepared as platforms to investigate the effects of the surface geometry and ionic strength on the protein adsorptive behavior. The surface geometry of the TiO₂ was found to play a dominant role in the protein adsorption capacity when the ionic strength of buffer solutions is very low. With the increase in ionic strength, the effect of the geometric structure on the protein adsorption capacity reduced greatly. The change of ionic strength has the highest significant effect on the mesoporous TiO₂ with large pore size compared with that with small pore size. The interaction between the protein and TiO₂ measured with atomic force microscopy further demonstrated that the adhesion force induced by the surface geometry reduced with the increase in the ionic strength. These findings were used to guide the detection of the retention behavior of protein by high-performance liquid chromatography, providing a step forward toward understanding the protein adsorption for predicting and controlling the chromatographic separation of proteins.