Protein Adsorption Kinetics on Silica: Theoretical Modeling and Experiments

Protein adsorption mechanism on silica/electrolyte interfaces was determined experimentally and by a thorough theoretical modeling. Primarily, the adsorption kinetics of myoglobin, albumins, and fibrinogen on a silica sensor under well-defined physicochemical conditions were investigated using the quartz microbalance method. Acquired results were scaled using adsorption kinetics derived from the random sequential adsorption modeling calibrated using atomic force microscopy (AFM) analysis of protein layers. The experimental results expressed in this way were interpreted in terms of the hydrodynamic theory, considering both a rigid and a soft, lubricated contact of molecules with the surface. The theory also furnished an analytical expression enabling the calculation of adsorption efficiency (impedance) for a broad range of protein sizes. It was demonstrated that the quartz microbalance measurements interpreted in terms of theoretical impedances pertinent to the contact agreed with analogous measurements derived from the reflectometric method. This allowed to confirm a nonlocalized and monolayer adsorption mechanism of the protein molecules controlled by electrostatic interactions.