The adsorption process of bovine serum albumin (BSA) onto a stainless steel surface was investigated using the quartz crystal microbalance based on admittance analysis. The adhered mass change ∆m increased with time as a result of contacting the BSA solution, and considerably long period (>2 h) was required for the attainment of the asymptotic values of ∆m as well as dissipation factor ∆D. The relation between ΔD and Δm suggested that the layer of adsorbed BSA molecules became stiffer with increasing time at higher BSA concentration. The relation between Δm after 2 h and the final BSA concentration was described well by the Langmuir adsorption isotherm. However, the time course of Δm clearly deviated from the Langmuir adsorption model. The stretched exponential function model described the time course of Δm well although it was an empirical one.
Keywords: QCM-A; bovine serum albumin; dissipation factor; protein adsorption; stretched exponential function.