Streptavidin‐polypyrrole Film as Platform for Biotinylated Redox Probe Immobilization for Electrochemical Immunosensor Application

Abstract A platform for construction of multi‐array electrochemical immunosensors was developed in which the measurement could be performed by various targets depending on the potential ranges of electrochemical detection. This was demonstrated by the immobilization of biotinylated redox molecules such as viologen and ferrocene, on modified polypyrrole‐streptavidin film. The polypyrrole film was modified by streptavidin layer, which serves for both the attachment of biotinylated redox marker and biotinylated antibody. Such biologically modified surface exhibits variation of electrochemical response of redox molecule at various potential ranges after antibody/antigen interaction. The measurement of redox signal of viologen and ferrocene was analyzed by differential pulse voltammetry (DPV) method and underlines a variation of redox properties upon the antigen interaction. Viologen immobilized on polypyrrole /streptavidin surface shows a redox signal at −1.2 V versus Ag/AgCl corresponding to the reduction of dicationic viologen to neutral viologen within 2 electrons process. Immobilized biotinylated ferrocene exhibits redox signal at 0.4 V versus Ag/AgCl. We demonstrate that when the biolayer bearing antibody is in contact with antigen, the redox signal of ferrocene or viologen was modified. The variation of current signal is directly related to the concentration of antigen in solution. A detection limit of pg.mL −1 was obtained demonstrating the sensitivity of such electrochemical immunosensor. The modified streptavidin polypyrrole surface bearing various biotinylated redox markers is a proof of concept for multi‐array electrochemical detection system of complex sample.