A SPR and AFM study of the effect of surface heterogeneity on adsorption of proteins

The effect of chemical heterogeneity of surfaces on the adsorption of proteins was investigated using model surfaces prepared by self-assembly of omega-functionalized alkanethiols on gold substrates. Surface plasmon resonance was used to monitor the adsorption kinetics of bovine serum albumin (BSA) and the morphology of the adsorbed BSA was imaged with tapping mode atomic force microscopy. The experiments show that the morphology of the adsorbed protein layer was altered significantly only when the surface heterogeneity was distributed in a patchwise manner on a nanometer length scale, which is commensurate with the dimension of the protein. In contrast to linear flexible polymers where the initial adsorption rate remained unchanged upon introduction of the chemical heterogeneity, the initial rate for the globular protein changed from the value observed on homogeneous surfaces and was dependent on the heterogeneous distribution of the chemical sites.