Studies towards the development of a screen-printed carbon electrochemical immunosensor array for mycotoxins:: A sensor for aflatoxin B1

Screen-printed carbon electrodes (SPCEs) bearing a surface-adsorbed antibody against aflatoxin B 1 (AFB 1) were used in a competitive immunoassay, based on competition of free analyte with a biotinylated aflatoxin B 1 conjugate. Subsequent addition of streptavidin-alkaline phosphatase (AP) conjugate, followed by a 1-naphthyl phosphate substrate resulted in the production of the electrochemically active product, 1-naphthol; this was oxidized using linear sweep voltammetry and constituted the measurement step. Investigations were carried out to test the suitability of reagents by enzyme-linked immunoassay (ELISA) and to deduce the optimum blocking agent for the immunosensors. Using the electrochemical immunosensor, a calibration plot for AFB 1 was obtained over the concentration range 0.15 to 2.5 ng/mL, giving a detection limit of around 0.15 ng/mL in buffer solution. The immunosensors were fabricated in an array configuration, suitable for use in conjunction with 96-well microtiter plates; indeed, each step of the immunoassay was performed by dipping the electrodes into microwells. These results represent the initial studies towards the development of an automated instrument for multi-analyte determinations using immunosensor arrays for mycotoxin detection and form the basis for further studies.