Quantitatively Elucidating the Trade-Off between Zwitterionic Antifouling Surfaces and Bioconjugation Performance

Zwitterionic materials, known for their high hydrophilicity, are widely used to minimize the nonspecific adsorption of biomolecules in complex biological solutions. However, these materials can also reduce the capture efficiency between targets and peptide probes. To demonstrate how antifouling surfaces affect capture efficiency, we utilize a poly(3,4-ethylenedioxythiophene) (PEDOT)-based surface incorporating varying ratios of phosphorylcholine (PEDOT-PC) and maleimide functional groups to achieve both antifouling properties and peptide–protein binding. As a model system, the peptide YWDKIKDFIGGSSSSC, attached via maleimide groups, is used to capture the target protein, calmodulin (CaM). By systematically monitoring protein binding on both antifouling and peptide-immobilized PEDOT surfaces using a quartz crystal microbalance with dissipation, the results reveal that PEDOT-PC reduces both the specific binding between peptides and target proteins as well as the rate of protein fouling on the electrode surface. From these findings, we propose an equation for quantitative analysis. Furthermore, electrochemical impedance spectroscopy and differential pulse voltammetry are performed to measure the changes in the impedance in CaM solutions. The data indicate that impedance increases with protein adsorption, confirming the practical utility of the designed electrode surface.