Submitted to: Gordon Research Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: June 19, 1999
Publication Date: N/A
Technical Abstract: Evanescent wave-based fiber-optic immunosensors were studied for the detection of fumonisins and aflatoxins in corn. An immunosensor using a competitive format was used to determine concentrations of the mycotoxin fumonisin B1 (FB1) in both spiked and naturally contaminated corn samples. Fumonisin antibodies were covalently coupled to an optical fiber and the competition between FB1 and FB1 labeled with fluorescein (FB1-FITC) for the limited number of binding sites on the fiber was assessed. The signal generated in the assay was inversely proportional to the FB1 concentration, with an IC50 of 70 ng/mL and a limit of detection of 10 ng/mL. The IC50 for samples depended upon the cleanup. For simple dilution of methanolic corn extracts the IC50 was equivalent to 25 ug FB1/g corn with a limit of detection of 3.2 ug/g corn, while with affinity column cleanup the IC50 was 5 ug FB1/g corn (limit of detection of 0.4 ug FB1/g). An HPLC method and the immunosensor method agreed well for naturally contaminated corn samples except when large amounts of other fumonisins that cross-react with the immunosensor were present. Using the native fluorescence of aflatoxin, a non-competitive assay for aflatoxin B1 (AFB1) was developed. This sensor, while capable of detecting as little as 2 ng/mL of AFB1 in solution was technically not an immunosensor, since the attachment of aflatoxin specific antibodies was not required. Sensors of the formats described have the potential to rapidly screen individual corn samples for fumonisins, but require coupling with a cleanup technique to be truly effective.