DETECTION OF THE MYCOTOXIN FUMONISIN B-1 BY A COMBINATION OF IMMUNOFLUORESCENCE AND CAPILLARY ELECTROPHORESIS

The specificity of antibodies has been combined with the speed and res olving power of capillary electrophoresis for application to the analy sis of the mycotoxin fumonisin BI (FB1). The assay was based upon the competition between unlabeled FBI (i.e. from a sample) and a fluoresce in-labeled FB1 reagent (FB1-FL). The FB1-FL was prepared by derivatizi ng FB1 with fluorescein isothiocyanate and was purified with affinity columns consisting of a monoclonal antibody (MAb) directed against fum onisins (clone P2A5-3-F3) coupled to agarose. The purified FB1-FL was subjected to capillary zone electrophoresis. Addition of purified MAb to FB1-FL before separation resulted in the formation of a complex (MA b FB1-FL) with resulting quenching of fluorescence and decrease in the intensity of the FB1-FL peak. When unlabeled FB1 was also added to th e reaction mixture the FB1 and FB1-FL competed for the limited amount of antibody present causing the FBI-FL peak to increase in direct prop ortion to the amount of unlabeled FBI present. Fumonisin standards cou ld be analyzed with this technique with a total analysis time of 6 min , 2 min of which was required for washing the capillary between analys es. The concentration of unlabeled FBI required to obtain 50% of the m aximum fluorescence (IC50) was highly dependent upon the antibody conc entration and ranged from 58 to 4170 ng ml(-1) at 15-75 mu g ml(-1) of antibody. The optimum performance was seen with 25-50 mu g ml(-1) of antibody, with IC50's between 500 and 1700 ng ml(-1) of FB1. The techn ique was applied to a limited number of corn samples spiked with high levels of FB1 (> 10 ppm). This technology holds considerable promise f or the rapid analysis of mycotoxins in foods.