Effect of surface hydrophobicity on adsorption and relaxation kinetics of albumin and fibrinogen: Single-species and competitive behavior

This work compares the spreading and relaxation rates of albumin and fibrin ogen, inferred from single-component and competitive adsorption kinetic exp eriments, on model. surfaces of varying hydrophobicity. Kinetics from the s ingle-component studies revealed a constant spreading rate, where the adsor bed protein footprint grew linearly in time for at least 15 min. This sprea ding rate increased with substrate hydrophobicity (ranging from 0.02 to 0.1 6 nm(2)/molecule/s for albumin and from 0.04 to 0.26 nm(2)/molecule/s for f ibrinogen), resulting in a larger extent of footprint growth and a lower ul timate coverage on hydrophobic surfaces when compared with hydrophilic surf aces at the same adsorption conditions. Competitive adsorption studies were in qualitative agreement with the single-component experiments but were ab le to probe longer spreading time scales. Although spreading appeared to oc cur initially at a constant rate in the competitive experiments, after 2 h the spreading rate had slowed dramatically and the spreading process had be gun to level off.