Characterization of self-assembled redox polymer and antibody molecules on thiolated gold electrodes

Abstract

Multilayer immobilization of antibody and redox polymer molecules on a gold electrode was achieved, as a strategy for the potential development of an amperometric immunosensor. The step-by-step assembly of antibiotin IgG on Os(bpy) 2ClPyCH 2NH poly(allylamine) redox polymer (PAH-Os) adsorbed on thiolated gold electrodes was proved by quartz crystal microbalance (QCM) and atomic force microscopy (AFM) experiments, confirming the electrochemical evidence. The increase of redox charge during the layer-by-layer deposition demonstrated that charge propagation within the layers is feasible. The multilayer structure proved to be effective for the molecular recognition of horseradish peroxidase–biotin conjugate (HRP–biotin), as confirmed by the QCM measurements and the electrocatalytic reduction current obtained upon H 2O 2 addition. The catalytic current resulting from PAH-Os mediation was shown to increase with the number of assembled layers. Furthermore, the inventory of IgG molecules on the supramolecular self-assembled structure and the specific and non-specific binding of HRP–biotin conjugate were confirmed by the QCM transient studies, giving information on the kinetics of IgG deposition and HRP–biotin conjugate binding to the IgG.