Immune-biosensor for aflatoxin B 1 based bio-electrocatalytic reaction on micro-comb electrode

Abstract

A new immunoassay concept for the determination of aflatoxin B 1 (AFB 1) based bio-electrocatalytic reaction on micro-comb electrode was proposed. The micro-comb electrode was fabricated by means of self-assembling horseradish peroxidase (HRP) and AFB 1 antibody molecules onto gold nanoparticles (nanogold) functionalized biorecognition surfaces. The presence of nanogold provided a congenial microenvironment for the immobilized biomolecules and decreased the electron transfer impedance, leading to a direct electrochemical behavior of the immobilized HRP. The formation of the antibody–antigen complex by a simple one-step immunoreaction between the immobilized anti-AFB 1 and AFB 1 in sample solution introduced a barrier of direct electrical communication between the immobilized HRP and the electrode surface, thus local conductivity variations could be detected by the HRP bio-electrocatalytic reaction in 0.02 M phosphate buffer solution (pH 7.0) containing 80 μM H 2O 2, 0.05 M KI and 0.15 M NaCl. Under optimal conditions, the proposed immune-biosensor exhibited a good conductometric response relative to AFB 1 concentration in a linear range from 0.5 to 10 ng/ml with a relatively low detection limit of 0.1 ng/ml at 3 δ. The developed immune-biosensor showed an acceptable accuracy compared with those obtained from ELISA. The inter-assay coefficients of variation are 7.1 and 4.6% at 1.0 and 8.0 ng/ml AFB 1, respectively. The storage stability is acceptable in a pH 7.0 phosphate buffer solution at 4 °C for 12 days. Importantly, the proposed methodology could be extended to the detection of other antigens or biosecurities.