Electrochemical Immunosensor Based on Polythionine/Gold Nanoparticles for the Determination of Aflatoxin B1

An aflatoxin B-1 (AFB(1)) electrochemical immunosensor was developed by the immobilisation of aflatoxin B-1-bovine serum albumin (AFB(1)-BSA) conjugate on a polythionine (PTH)/gold nanoparticles (AuNP)-modified glassy carbon electrode (GCE). The surface of the AFB(1)-BSA conjugate was covered with horseradish peroxidase (HRP),in order to prevent non-specific binding of the immunosensors with ions in the test solution. The AFB(1) immunosensor exhibited a quasi-reversible electrochemistry as indicated by a cyclic voltammetric (CV) peak separation (Delta E-p) value of 62 mV. The experimental procedure for the detection of AFB(1) involved the setting up of a competition between free AFB(1) and the immobilised AFB(1)-BSA conjugate for the binding sites of free anti-aflatoxin B-1 (anti-AFB(1)) antibody. The immunosensor's differential pulse voltammetry (DPV) responses (peak currents) decreased as the concentration of free AFB(1) increased within a dynamic linear range (DLR) of 0.6 - 2.4 ng/mL AFB(1) and a limit of detection (LOD) of 0.07 ng/mL AFB(1). This immunosensing procedure eliminates the need for enzyme-labeled secondary antibodies normally used in conventional ELISA-based immunosensors.