A rapid colloidal gold-based immunochromatographic strip assay for monitoring nitroxynil in milk.

ABSTRACT

BACKGROUND: Nitroxynil (NIT) is a veterinary drug against hepatic fluke disease for food-producing cattle and sheep. NIT has a long half-life time in animals since it is highly bound to plasma protein. Therefore NIT possibly remains in animal edible tissues or milk due to drug abuse. In this study, a specific murine monoclonal antibody (mAb) against NIT was prepared and an immunochromatographic strip assay based on the mAb was developed for screening NIT in milk. RESULTS: The affinity constant of the anti-NIT mAb was 2.93 × 1010 and the anti-NIT mAb had almost no cross-reactivity with other analogs, so that it showed good specificity. The cutoff value of this test strip was considered to be 50 ng mL-1 by the naked eye. When detected by the strip reader, the half maximum inhibition concentration (IC50 ) of the immunoassay strip was calculated to be 5.716 ng mL-1 and the limit of detection (LOD) was 1.146 ng mL-1 . Intra-assay recoveries from 88.80 to 97.13% were obtained, with the highest coefficient of variation (CV) at 9.01%; inter-assay recoveries ranged from 84.60 to 106.87%, with the highest CV at 9.93%. CONCLUSION: The operative procedure of the proposed method can be completed within 10 min. The strip developed in this study was a practical tool for rapid semiquantitative and quantitative detection of NIT in milk. This study suggested great potential for analytically monitoring NIT in other food samples. © 2019 Society of Chemical Industry.