Fluorescence polarization as a tool for the determination of deoxynivalenol in wheat

The mould Fusarium graminearum is found worldwide as a pathogen of cere;d grains. in pa;·ticular of wheat and maize. and it produces a mycotoxin known as deoxvnivalenol (DON or vomitoxin). Each veal', the !Jre~~nce of this compound and related trich~thecenes causes substantial losses to agricultural productivity. Rapid methods for the measurement of the toxin in grains are required to monitor and divert effectively contaminated grain Fom the food supply. A fluorescence polarization (FP) immunoassay using a previouslv described monoclonal antibodv for DON was devel~ped. The assay was based on t/;e 'competition of unlabeled DON fi'om a sample with a fluorescently tagged DON. DON:fluorescein (DON-FL) , for a DON-specific monoclonal antibody in solution. The FP of the tagged DON was increased upon binding with the antiboc(v. In the presence offi'ee toxin, less of the DON-FL was bound and the polarization signal was decreased. The assays were very simple to pelfonn, requiring only mixing of an aqueous extract of wheat with the DON-FL and antibody. The sensitivity of the assay was strongly dependent upon the time between mixing of the sample with the tracer and measurement of the fluorescence polarization, with midpoints for the competition curves ranging from 0.03 f-lg ml-1 with a !5-s incubation to >I ~Lg ml-1 lvith a 12-min incubation. Samples of wheat naturally contaminated lvith DON were evaluated bv FP and bv an HPLC-UV method. with a good con:elation (r2 ~ 0.97). Although the FP method tended to overestimate DON slightly in