Enzyme modified peptide nanowire as label for the fabrication of electrochemical immunosensor

Ferrocene (Fc) functionalized self-assembled peptide nanowire (Fc-PNW) was synthesized, functionalized and used as label for the fabrication of electrochemical immunosensors to detect substance P (SP). To prepare the label, gold nanoparticles (AuNPs) were immobilized onto the Fc-PNW for the following adsorption of horseradish peroxidase (HRP) and secondary anti-SP antibody (Ab(2), Fc-PNW-HRP-Ab(2)). The role of Fc-PNW in the electrochemical label was not only as supporting matrix for HRP and Ab(2), but also as the mediator for HRP to enhance the sensitivity of HRP toward H2O2 detection. The immunosensor was fabricated based on the traditional sandwich protocol with primary anti-SP antibody (Ab(1)) immobilized onto graphene surface. The catalytic current of HRP toward H2O2 in the presence of mediator Fc was used as signal of the immunosensor. Different parameters, such as the weight ratio of HRP to Ab(2) on the Fc-PNW and the antibody-antigen incubation time were optimized to improve the performance of the immunosensor. The resulting immunosensor has high sensitivity, wide linear range (0.01-50 ng/mL) and low detection limit (5 pg/mL). (C) 2014 Elsevier B. V. All rights reserved.