Electrochemical immunosensor for the detection of staphylococcal enterotoxin B using screen-printed electrodes

Abstract

Staphylococcal enterotoxin B (SEB) is responsible for large number of food poisoning cases throughout the world. SEB is an exotoxin and it is one of the several harmful substances produced by the bacterium <em>Staphylococcus aureus</em>. Therefore, it is required to develop methods for the sensitive, reliable, reproducible, cheaper, easy to use and rapid detection of SEB. An electrochemical immunosensor has been studied for the fast detection of SEB using disposable screen-printed electrodes. Ascorbic acid-2-phosphate (AA-2P) is used as a new substrate for the voltammetric detection of SEB. In the alkaline buffer solution the alkaline phosphate (ALP) enzymatic hydrolysis product of AA-2P is ascorbic acid (AA). Ascorbic acid is an electroactive substance and gives differential pulse voltammetric oxidative response at +380 mV (versus Ag/AgCl). The potential +0.39 V corresponds to the oxidation of AA. Indirect sandwiched enzyme linked immunosorbent assay (ELISA) has been used for the detection of SEB. In this method, anti-rabbit IgG for SEB (capturing antibody) is first immobilized on the surface of SPE followed by reacting with SEB (antigen) to form antigen-antibody complex. After that, anti-mice IgG for SEB (secondary antibody) are added, followed by ALP-conjugated anti-mice IgG (revealing antibody). The optimal conditions for ALP enzymatic reaction and the volumetric detection have been optimized. It is found that the response of voltammetric immunosensor is proportional to the SEB concentration in the range 0.1–100 ng/mL and the detection limit was found to be 0.1 ng/mL.