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.