Nanoscale organization of human serum albumin at model cytocompatible surfaces

Scanning force microscopy (SFM) operating in tapping mode was used to study the interaction of a model protein, human serum albumin (HSA), with oxidized polystyrene surfaces. HSA adsorption and organization were investigated as a function of incubation time. A fast adsorption was observed onto protein-free surfaces leading to a complete coverage in few seconds with a protein concentration of 1 mg/ml. The formation of a first protein layer give rise to a relatively hydrophilic surface as measured by nanoscale force spectroscopy (SFM force–distance curves) and confirmed on macroscopic scale by contact angle measurements. This protein layer is supposed to be the basic frame for the observed growth of low dimensional (2D) densely packed systems that are formed at long incubation times. These findings are interpreted in terms of the molecule–surface interaction forces and molecular surface diffusion processes. The influence of the protein lateral packing on the SFM imaging is also discussed.