Fiber-Optic Immunosensor for the Detection of Fumonisin B₁

A fiber-optic immunosensor was developed to measure the mycotoxin fumonisin B 1 (FB 1 ). Monoclonal antibodies produced against FB 1 were covalently bound through a heterobifunctional silane to an etched 800 μm core optical fiber. An evanescent wave effect was utilized to excite fluorescein isothiocyanate labeled FB 1 (FB 1 -FITC) molecules near the surface of the fiber. A direct competitive assay was used to measure FB 1 concentrations with the following steps: saturation of antibody binding sites by FB 1 -FITC, competition of FB 1 and FB 1 -FITC with displacement of the labeled toxin, and resaturation of binding sites by FB 1 -FITC. The signal generated in the assay was found to be inversely proportional to the FB 1 concentration. This sensor exhibited a working range of 10−1000 ng of FB 1 /mL, an IC 50 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 FB 1, sphinganine, or tricarballylic acid. Sensor performance was also found to be unaffected in a sample matrix of methanol/water-extracted corn.