Potential-assisted adsorption of bovine serum albumin onto optically transparent carbon electrodes

Abstract

This article describes the effect of the applied potential on the adsorption of bovine serum albumin (BSA) to optically transparent carbon electrodes (OTCE). To decouple the effect of the applied potential from the high affinity of the protein for the bare surface, the surface of the OTCE was initially saturated with a layer of BSA. Experiments described in the article show that potential values higher than +500 mV induced a secondary adsorption process (not observed at open-circuit potential), yielding significant changes in the thickness (and adsorbed amount) of the BSA layer obtained. Although the process showed a significant dependence on the experimental conditions selected, the application of higher potentials, selection of pH values around the isoelectric point (IEP) of the protein, high concentrations of protein, and low ionic strengths yielded faster kinetics and the accumulation of larger amounts of protein on the substrate. These experiments, obtained around the IEP of the protein, contrast with the traditional hypothesis that enhanced electrostatic interactions between the polarized substrate and the (oppositely charged) protein are solely responsible for the enhanced adsorption. These results suggest that the potential applied to the electrode is able to polarize the adsorbed layer and induce dipole-dipole interactions between the adsorbed and the incoming protein. This mechanism could be responsible for the potential-dependent oversaturation of the surface and could bolster to the development of surfaces with enhanced catalytic activity and implants with improved biocompatibility.