Rapid detection of aflatoxin B(1) 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 B(1) (AFB(1)) immunoassay. Dot-immunogold filtration assay (DIGFA) of AFB(1) on NCM was developed in this study. At first, the colloidal gold was synthesized and colloidal gold-monoclonal antibody (McAb) conjugates against AFB(1) were prepared at pH 7.0 of colloidal gold solution, 0.018mg/mL of McAb. Then the colloidal gold-McAb conjugates were used to develop AFB(1) DIGFA, which detection time was only 15min, six times less than that of ELISA. With this method to determine the standard AFB(1) solution, the results demonstrated a visual detection limit of approximately 2ng/mL of AFB(1), which was similar to that of ELISA. This method had good specificities for AFG(1), AFG(2) and AFM(1) and a little cross-reactivity with AFB(2). 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 AFB(1) in foods in the field within 15min without complicated steps.