Magnetic nanogold microspheres-based lateral-flow immunodipstick for rapid detection of aflatoxin B2 in food.

A novel membrane-based lateral-flow immunodipstick assay was developed for the fast screening of aflatoxin B(2) (AFB(2)) as a model compound in food samples. The detector reagent consisted of magnetic nanogold microspheres (MnGMs) with nano-Fe(2)O(3) particles as core and gold nanoparticles as shell, and bio-functionalized with monoclonal anti-AFB(2) antibodies. Manually spotted AFB(2)-bovine serum albumin conjugates (AFB(2)-BSA) and goat anti-mouse IgG on nitrocellulose membrane were used as test and control lines, respectively. As the major advantage, experimental results indicated that the visual detection limit (cutoff value) of the MnGM-based dipstick immunoassay with 0.9 ng/ml AFB(2) was about threefold lower compared to a conventional immunodipstick test using gold nanoparticles as detection reagent. Qualitative results (yes/no) could be obtained within 15 min without expensive equipment. The assay was evaluated with AFB(2) spiked or naturally contaminated samples (n=8), including peanuts, hazelnuts, pistacia and almonds, receiving excellent correspondance with results from high performance liquid chromatography (HPLC). Most importantly, the assay gave no false negative results. By controlling the target antibody this assay can be easily extended for use with other food relevant toxins and thus represents a versatile detection method.