Electrochemical studies of the adsorption behavior of bovine serum albumin on stainless steel

The adsorption behavior of bovine serum albumin (BSA) on high-purity austenitic levy-carbon stainless steel and its effect on the state of the electrode surface have been studied over the temperature range 299-343 K under open-circuit-potential conditions, using electrochemical impedance spectroscopy (EIS). The impedance spectra were interpreted in terms of an equivalent electrical circuit (EEC) based on a possible physical model with the circuit elements representing the electrochemical properties of the investigated system. The adsorption of BSA onto the stainless steel surface resulted in an increased rate of metal dissolution, i.e., corrosion. The plateau values of corrosion rate were achieved after a "threshold" BSA concentration in the bulk solution at all the temperatures studied. The rate of the corrosion process was found to be controlled by both the surface diffusion and charge transfer process. Adsorption of BSA onto the stainless steel sur face was described with a Langmuir adsorption isotherm. The thermodynamic data were calculated to give the corrosion activation energy, Gibbs free energy, enthalpy, and entropy of adsorption. The data suggested a very strong adsorption of BSA molecules, accompanied by a charge transfer mechanism involving chemisorption. An adsorption mechanism was proposed involving the interaction of the negatively charged carboxylate groups of the proteins with the stainless steel surface. The EIS technique was shown to be a valuable tool in studying the interfacial behavior of proteins at metal electrode surfaces.