Electrode Surface Potential-Driven Protein Adsorption and Desorption through Modulation of Electrostatic, van der Waals, and Hydration Interactions

Abstract

When proteins in aqueous solutions are exposed to solid substrates, they adsorb due to the dynamic interplay of electrostatic, van der Waals, and hydration interactions and do so in a rather irreversible fashion, which makes protein recovery troublesome. Here, we use a gold electrode as the solid substrate and modulate the surface potential to systematically induce protein adsorption as well as partial desorption. We use different methods such as surface plasmon resonance, atomic force microscopy, and electrowetting and show that biasing the electrode to more negative potentials (by −0.4 V compared to the open-circuit potential at pH 6) results in an increased adsorption barrier of 6 kJ mol–1 for the negatively charged protein β-lactoglobulin. Further, we clearly demonstrate that this is due to an increased double layer potential of −0.06 V and an increase in hydration repulsion. This indicates that an electric potential can directly influence surface interactions and thus induce partial β-lactoglobulin desorption. These observations can be the basis for biosensors as well as separation technologies that use only one trigger to steer protein ad- and desorption, which is low in energy requirement and does not generate large waste streams, as is the case for standard protein separation technologies.

The Decisive Role of Li2O2 Desorption for Oxygen Reduction Reaction in Li–O2 Batteries

“…After the desorption process of Li 2 O 2 *, I (Li 2 O 2 ) gradually declines to a steady level rather than zero value, where a small SERS peak is observed at 790 cm –1 at the end of the OCP process (Figure S5), indicating that desorbed Li 2 O 2 species are still located near the electrode surface. This result proves the desorption process of insoluble Li 2 O 2 * is occurring in the subnanometer SERS observation region near the electrode surface, , different from the diffusion of soluble species. Meanwhile, the steady nonzero value of I (Li 2 O 2 ) at the end of the OCP process indicates the decline of I (Li 2 O 2 ) is not related to the spontaneous degradation of Li 2 O 2 with time, which would cause the disappearance of Li 2 O 2 peaks.…”

“…and metal substrates are not fully understood. The desorption (detachment) of insoluble metal oxides , and proteins from the electrode surface has been previously proposed. − …”

Dielectric Spectroscopy Can Predict the Effect of External AC Fields on the Dynamic Adsorption of Lysozyme

“…[12][13][14][15][16][17][18] This phenomenon is particularly important because it could open the door for the possibility to control the efficiency, selectivity, and kinetics of the adsorption process. [19] Illustrating the intriguing complexity of the adsorption process, several authors have linked the effect of the potential applied to a surface with electrostatic interactions, [20][21][22][23] orientation, [14,24,25] as well as hydration of the protein. [26] Following pioneer work by Kirkwood and Shumaker, [27] several authors have explored the possibility to affect the charge and charge distribution of proteins via external fields.…”

“…[19] Illustrating the intriguing complexity of the adsorption process, several authors have linked the effect of the potential applied to a surface with electrostatic interactions, [20][21][22][23] orientation, [14,24,25] as well as hydration of the protein. [26] Following pioneer work by Kirkwood and Shumaker, [27] several authors have explored the possibility to affect the charge and charge distribution of proteins via external fields. This process seems to correlate with the slope of the pH titration curve [28] and that can be rationalized consider-ing the protein's charge capacitance.…”

“…On conducting substrates, an external applied potential can also be used to control the accumulation of the protein molecules at the polarized interface [12–18] . This phenomenon is particularly important because it could open the door for the possibility to control the efficiency, selectivity, and kinetics of the adsorption process [19] . Illustrating the intriguing complexity of the adsorption process, several authors have linked the effect of the potential applied to a surface with electrostatic interactions, [20–23] orientation, [14,24,25] as well as hydration of the protein [26] .…”