Direct Measurement of Protein Adhesion at Biomaterial Surfaces by Scanning Force Microscopy

The adsorption of human serum albumin (HSA) onto tailor-made polyurethane biomaterial coatings was measured in a liquid environment by scanning force microscopy (SFM). The adhesion of HSA onto polyurethane films was probed by adhesion force measurements with protein-coated SFM tips. Results reveal that HSA adsorbs readily onto hydrophobic polyurethane surfaces. Adsorption time profiles of the HSA deposition were elucidated by dynamic in situ force-distance measurements. The introduction of poly(ethylene glycol) (PEG) grafts, present at the biomaterial interface, inhibited all interactions with HSA. Latter results were explained by the combined effects of steric repulsion forces, minimal interfacial free energy, and high chain mobility of the hydrated PEG grafts. These phenomena were in excellent agreement with measurements obtained in surface plasmon resonance experiments.