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Development of an indirect competitive enzyme-linked immunosorbent assay and immunochromatographic assay for hydrocortisone residues in milk

Wang, Zhongxing, Xie, Zhengjun, Cui, Gang, Liu, Liqiang, Song, Shanshan, Kuang, Hua, Xu, Chuanlai
Food and agricultural immunology 2017 v.28 no.3 pp. 476-488
cortisol, cross reaction, detection limit, enzyme-linked immunosorbent assay, haptens, immunoaffinity chromatography, inhibitory concentration 50, milk, monoclonal antibodies
An anti-hydrocortisone (HDS) monoclonal antibody, 2G8, based on a HDS succinic anhydride derivative hapten, was prepared and used to develop an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) and an immunochromatographic assay for the detection of HDS in milk samples. The half inhibitory concentration (IC ₅₀) of the antibody was 0.095 ng/mL, its limit of detection was 0.013 ng/mL, its linear range of detection was 0.026–0.356 ng/mL, and its cross-reactivity with HDS analogs was <5%. In spiked samples and a recovery test, the recovery rates ranged from 92% to 98.5%, indicating the suitability of this ic-ELISA for the analysis of HDS in milk. The immunochromatographic strip had a cutoff value of 2 ng/mL in milk and could be used for the semiquantitative analysis of HDS. When milk samples were added to the sample pad of the strip, a bright test line indicated <0.2 ng/mL HDS, a weak test line indicated 0.2–2 ng/mL HDS, and no test line indicated ≥2 ng/mL HDS. Analysis of HDS in milk samples showed that results acquired by the immunochromatographic assay agreed well with results acquired by ic-ELISA. Thus, the ic-ELISA and strip assay developed in this study rapidly and sensitively detect HDS residues in milk samples.