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An ultra-sensitive monoclonal antibody-based fluorescent microsphere immunochromatographic test strip assay for detecting aflatoxin M1 in milk

Zhang, Xiya, Wen, Kai, Wang, Zhanhui, Jiang, Haiyang, Beier, Ross C., Shen, Jianzhong
Food control 2016 v.60 pp. 588-595
aflatoxin M1, antigens, cross reaction, detection limit, fluorescence, immunoaffinity chromatography, immunoassays, inhibitory concentration 50, milk, monoclonal antibodies
A rapid lateral flow fluorescent microsphere immunochromatographic test strip (FM-ICTS) assay has been developed for the detection of aflatoxin M1 (AFM1) residues in milk. For this purpose, an ultra-sensitive anti-AFM1 monoclonal antibody (MAb) 1D3 was prepared and identified. The IC50 value of the MAb 1D3 for AFM1 was 23 ng/L, and the cross-reactivity (CR) of the MAb with aflatoxin M2, aflatoxin B1, aflatoxin B2, aflatoxin G1 and aflatoxin G2 was 18%, 9%, <0.15%, 43% and <0.3%, respectively. The MAb was covalently conjugated with carboxylate-modified FMs, and the FMs were used as the label in a competitive immunochromatography assay. Using a moderate hapten-to-protein coupling ratio (˜2) in the coating antigen resulted in improved immunoassay sensitivity. Under optimal conditions, the IC50 value of the assay was 36.3 ng/L with the limit of detection (LOD) of 4.4 ng/L in milk samples using a fluorescence reader, and the recoveries of AFM1 in spiked milk samples ranged from 76.6 to 110.8% with coefficient of variation (CV) of 4–14.7%. The whole procedure could be completed within 30 min. The results demonstrated that the FM-ICTS assay is easy to conduct, rapid, highly sensitive and specific for the detection of AFM1 residues in milk.