A portable fluorescent microsphere-based lateral flow immunosensor for the simultaneous detection of colistin and bacitracin in milk.

The polypeptide antibiotics colistin (COL) and bacitracin (Baci) are extensively used as veterinary drugs and feedstock additives in the livestock industry, which inevitably causes residues in animal-origin food, which can accelerate human tolerance to antibiotics. In this study, a portable lateral flow immunoassay (LFIA) for the simultaneous determination of COL and Baci residues in milk was developed. The replacement of gold nanoparticles used in the traditional LFIA with fluorescent microspheres (FMs) to label monoclonal antibodies (mAbs) allowed qualitative and quantitative analyses within a few minutes. Based on the principle of competitive binding to FM-labelled mAbs between analytes in samples and fixed antigens on the membrane, the assay provided qualitative cut-off values of 100 and 50 ng mL-1 for Baci and COL in milk samples. Furthermore, a strip reader-based semi-quantitative detection system could detect lower limits of 7.85 and 1.89 ng mL-1 for Baci and COL, respectively. In conclusion, the proposed multiplex LFIA immunosensor provides an auxiliary analytical tool for the rapid and simultaneous screening of COL and Baci in large cohorts of samples.

Development of an ic-ELISA and Immunochromatographic Strip Assay for the Detection of Diacetoxyscirpenol in Rice.

Diacetoxyscirpenol (DAS) is a highly toxic type A trichothecene, a natural contaminant in food and animal feed, which is a serious hazard to human and animal health. An anti-DAS mAb, 3H10, with high sensitivity and specificity, was prepared, and an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) and a lateral-flow immunochromatographic strip (ICA strip) were developed for rapid testing of DAS in rice samples. The 50% inhibitory concentration and limit of detection of ic-ELISA were 5.97 and 0.78 ng/mL, respectively. The recovery of rice samples ranged from 99.4 to 110.7%, demonstrating that the analytical method can be used to detect rice samples. The cutoff value of the lateral-flow ICA strip to DAS was 500 ng/g. The developed immunoassay method can provide an effective method of initially detecting and screening DAS in food and feed samples.