Electrochemical Impedance Spectroscopy Using Interdigitated Gold-Polypyrrole Electrode Combination

A novel electrochemical impedance spectroscopy (EIS) sensor design, based on a standard interdigitated electrode arrangement in which the working electrode consists of gold and the combined counter and reference electrodes of polypyrrole doped with polystyrene sulfonate (PPy:PSS), is evaluated for biosensing applications. The performance is successfully proved by immobilization of a thiolated biotin as a self-assembled monolayer (SAM), followed by streptavidin and a biotinylated horseradish peroxidase. It is shown that specific binding of biomolecules takes place only at the gold electrode. The binding activities are not influenced by the addition of small amounts of the nonionic surfactant Pluronic F-68. The immobilization process is monitored online with EIS showing an excellent repeatability of the EIS signals in comparison with Au-Au electrode configuration even after electrode regeneration.