Fiber-optic immunosensor for the detection of fumonisin B-1

A fiber-optic immunosensor was developed to measure the mycotoxin fumonisin B-1 (FB1). Monoclonal antibodies produced against FB1 were covalently bound through a heterobifunctional silane to an etched 800 mu m core optical fiber. An evanescent wave effect was utilized to excite fluorescein isothiocyanate labeled FB1 (FB1-FITC) molecules near the surface of the fiber. A direct competitive assay was used to measure FB1 concentrations with the following steps: saturation of antibody binding sites by FB1-FITC, competition of FB1 and FB1-FITC with displacement of the labeled toxin, and resaturation of binding sites by FB1-FITC. The signal generated in the assay was found to be inversely proportional to the FB1 concentration. This sensor exhibited a working range of 10- 1000 ng of FB1/mL, an IC50 of 70 ng/mL, and a limit of detection of 10 ng/mL. These values compared favorably with those for currently available ELISA techniques. The sensor exhibited cross-reactivity with fumonisin B-2 but did not react with hydrolyzed FB1, sphinganine, or tricarballylic acid. Sensor performance was also found to be unaffected in a sample matrix of methanol/water-extracted corn.