Influence of potential on the adsorption of a material binding peptide on Au via EIS and in-situ fluorescence imaging

Creating well-defined peptide modified electrode surfaces facilitates the development of electrochemical processes that rely on surface modification by adsorbed biomolecules. Control over the adsorption of material-binding peptides (MBP) require methods to assess the interfacial characteristics of the adsorbed layer. While MBP have been harnessed in diverse applications, existing methods for quantifying the potential dependence of peptide adsorption are limited. Here, we present a method that uses electrochemical impedance spectroscopy (EIS) for characterizing MBP adsorption onto a gold electrode. This approach uses EIS to measure the interfacial capacitance which is converted into peptide coverage using a two-state model. The potential dependent coverage is used to calculate adsorption energy as a function of the applied potential. This approach was demonstrated by characterizing an MBP adsorbed onto a gold electrode and showing the stability of the adsorbed peptide as a function of electrode potential, defining the potential where desorption occurs. The model and approach was supported by ex-situ AFM of a monolayer and high coverage multilayer of adsorbed MBP in addition to in-situ fluorescence microscopy under electrochemical conditions using a fluorophore-labeled MBP. The EIS approach used to characterize the peptide-modified gold electrode may be useful for characterizing other biomaterials and substrates.