Development of an immunochromatographic assay for detection of tylosin and tilmicosin in muscle, liver, fish and eggs

An immunochromatographic assay (ICA) was developed and applied for the residue determination of tylosin and tilmicosin in muscle, liver, fish and eggs. The assay is based on a competitive format, and its sensitivity is improved by using a novel criterion to screen the optimal amount of nanogold-labelled monoclonal antibody. Owing to the novel nanogold particle labelling method, 10 min was sufficient to perform the ICA, the visual detection limits were 10 and 20 ng/g for tylosin and tilmicosin, respectively. The standard curves based on the tylosin and tilmicosin matrix calibration ranged from 0.1 to 100 ng/mL, with IC₅₀ values of 2.9 and 4.1 ng/mL for tylosin and tilmicosin, respectively. The recovery rates ranged from 71.5 to 103.2%, with coefficient of variation <14.1%, when tylosin and tilmicosin were spiked in various biological matrices with the concentrations of 10–100 ng/g. The results of ICA were consistent with those of ELISA kit and high-performance liquid chromatography in the analysis of tylosin in the incurred tissues, demonstrating the practical applicability of the developed assay in real samples. Over all, to our knowledge, this is the first report of qualitative and semi-quantitative residue determination for tylosin and tilmicosin by ICA.