Mechanism of HSA adsorption on mica determined by streaming potential, AFM and XPS measurements

Adsorption of human serum albumin (HSA) on mica at pH 3.5 (0.15 M NaCl) was studied using in situ streaming potential measurements, AFM imaging and XPS. Results obtained by streaming potential were consistent with AFM measurements and theoretical predictions based on the random sequential adsorption model. These results in combination with complementary data derived from XPS allowed one to determine both the kinetics of adsorption and the maximum coverage of irreversibly bound HSA, which was close to 1.6 mg m−2 (dimensionless coverage 0.45). It was concluded that HSA adsorption on mica at pH 3.5 occurred under side-on, electrostatically controlled mechanisms with no tendency to multilayer formation. Such irreversible bound HSA monolayers of well-defined coverage can find applications for performing efficient immunological tests, designing biomaterials surfaces and biosensors.