A colorimetric method was developed for the determination of the mold toxin fumonisin B1 (FB1). It is based on the aggregation of cysteamine-capped gold nanoparticles (Cys-AuNPs). The assay involves alkaline hydrolysis of FB1 to obtain hydrolyzed fumonisin B1 (HFB1). The latter induces the aggregation of Cys-AuNPs which results in a color change from wine-red to blue-gray, best at a pH value of 9.0. A plot of absorbance ratio at 645/520 nm versus FB1 concentration is linear in the 2-8 μg kg-1 FB1 concentration range, and the detection limit is 0.90 μg kg-1. Inter-day and intra-day precisions are <6.2%, and recoveries from spiked samples ranged from 93 to 99%. The assay was successfully applied to the determination of FB1 in corn samples. It has a high selectivity over other competitive mycotoxins including aflatoxin, zearalenone, citrinin and patulin. The method is more selective than the detection of FB1 directly which may lead to false-positive errors. Graphical abstract Schematic representation of colorimetric assay of fumonisin B1 (FB1). FB1 was alkali-hydrolyzed and its product (hydrolyzed fumonisin B1) induces cysteamine-capped gold nanoparticles (Cys-AuNPs) via hydrogen bondings. The aggregation of Cys-AuNPs causes changes in color from wine-red to blue-gray.
Keywords: Corn; Mycotoxin; Noble metals; SPE; UV-Vis.