SURFACE HYDROPHOBIC INFLUENCES ON BETA-LACTOGLOBULIN ADSORPTION-KINETICS

The adsorption isotherms and kinetic behavior exhibited by β-lactoglobulin at silanized silicon surfaces of varying hydrophobicity were examined using ellipsometry. Adsorption isotherms indicated that the adsorbed mass of β-lactoglobulin increased with increasing surface hydrophobicity, within a defined range of hydrophobicity. Adsorption kinetics recorded for β-lactoglobulin on each surface were compared to the kinetic behavior predicted by a simple model for protein adsorption. The model described the data well in all cases, enabling interpretation of the kinetic behavior in terms of contact surface hydrophobicity influences on rate constants affecting protein attachment and unfolding at the interface. In particular, both experimental and simulation results seem to be in support of a hypothesis that rate constants defining protein arrival and conversion to an irreversibly adsorbed state increase with increasing surface hydrophobicity, while the rate constant defining desorption of protein from a reversibly adsorbed state decreases with increasing surface hydrophobicity. Contact surface hydrophobicity was quantified using contact angle analysis to determine the nondispersive component of the work required to remove water from unit area of surface. Quantitative consideration of possible mass transfer influences on the observed adsorption rates supports the notion that the experiments were not conducted in a transport-limited regime. © 1992.