Rapid detection of aflatoxin B1 on membrane by dot-immunogold filtration assay

Immunofiltration assay for mycotoxins in which nitrocellulose membrane (NCM) was used as a support and enzyme was used as the label has been developed since the late 1980s. As colloidal gold is a good labeling substance that can accelerate antibody–antigen reaction which result can be read directly by naked eyes, the colloidal gold particles could replace the enzyme to be labeled to antibody in aflatoxin B1 (AFB1) immunoassay. Dot-immunogold filtration assay (DIGFA) of AFB1 on NCM was developed in this study. At first, the colloidal gold was synthesized and colloidal gold-monoclonal antibody (McAb) conjugates against AFB1 were prepared at pH 7.0 of colloidal gold solution, 0.018 mg/mL of McAb. Then the colloidal gold-McAb conjugates were used to develop AFB1 DIGFA, which detection time was only 15 min, six times less than that of ELISA. With this method to determine the standard AFB1 solution, the results demonstrated a visual detection limit of approximately 2 ng/mL of AFB1, which was similar to that of ELISA. This method had good specificities for AFG1, AFG2 and AFM1 and a little cross-reactivity with AFB2. 45 food samples collected from the markets were subjected to DIGFA and the results showed that one corn sample was positive and in agreement that of HPLC. It is suggested that DIGFA developed in current study has a potential use as a rapid and cost-effective screening tool for the determination of AFB1 in foods in the field within 15 min without complicated steps.