Surface electric field manipulation of the adsorption kinetics and biocatalytic properties of cytochrome c on a 3D macroporous Au electrode

Upon adsorbing on a solid-state substrate, water-soluble proteins are prone to denaturation and deterioration of their functions due to the conformation change. The surface electric field of a conductive substrate is one of the important factors that influence the character of adsorbed proteins. In this work, a 3D macroporous gold electrode has been prepared and served as the working electrode to study the influence of surface electric field on the adsorption kinetics and conformation of the adsorbed cytochrome c (cyt-c) with the help of electrochemical, in situ electrochemical IR spectroscopic, atomic force microscopic, and contact angle measurements. The external electric field creates excess surface charge which can manipulate the adsorption rate of proteins on the substrate by the enhanced electrostatic interactions between the electrode and protein patches by coupling with complementary charges. The amount of immobilized cyt-c with electrochemical activity on the 3D macroporous gold electrode showed a minimum at potential of zero charge (PZC) and it increased with increasing net excess surface charge. Higher electric field could influence the conformation and the corresponding properties such as direct electrochemistry, bioactivity, and surface character of the adsorbed cyt-c molecules. However, high external electric field leads to damage of the protein secondary structure. This study provides fundamentals for the fabrication of biomolecular devices, biosensors, and biofuel cells through electrostatic interactions. Figure Two cases are illustrated for the protein immobilized on electrode surfaces: a retention of protein structure under moderate excess surface charge, b denaturation and conformation change of proteins adsorbed at high excess surface charge, e.g., due to the higher external electric field.