Abstract: In this paper, an amplified immunosensor with highly sensitivity has been proposed based on precipitation of an insoluble product on functionalized electrode. Anti-hIgG was immobilized onto the surface of gold electrode modified with 1,6-hexanedithiol and colloidal Au interface. It was proved that the amount of immobilized antibody and the immunoactivity of bound antibodies could be well improved by colloidal Au. HRP labeled antibody reacted with antigen, then HRP biocatalyzed DAB (3,3′-diaminobenzidine) in the presence of H₂O₂, resulting in an insoluble product on the electrode surface, to achieve an obviously decreased frequency. Comparing with the direct detection of antigens, the immunosensor with the proposed amplified procedure shows improved sensitivity due to the significantly extended detection range. Analytical results indicate that the developed amplified procedure is a promising alternative for biorecognition element on the electrode surface showing an improved performance in terms of the magnitude of the response and sensitivity. The proposed immunosensor in optimal conditions has a linear range of 16 ng/mL-100 μg/mL for hIgG detection with a detection limit of 10 ng/mL. The immunosensor can be used to quantitatively determine hIgG in the sample of human serum.

Key words: Enzyme-biocatalyzed amplification, Colloidal Au, 1,6-Hexanedithiol self-assemble, Piezoelectric immunosensor