Development of a lateral-flow immunochromatographic test device for the rapid detection of difloxacin residues

In this study, a rapid competitive immunochromatographic test strip has been developed for specifically testing residues of difloxacin (DIF). 1H₁₀-2B₂, one of the three hybridoma lines that were tested and selected by enzyme linked immunosorbent assay, was used in the test strip. The monoclonal antibody has a good sensitivity with an IC₅₀ of 2.2 ng/mL to DIF, 0.24% cross-reactivity towards danofloxacin and no cross-reactivity towards other related compounds and other drugs. The calibration curve of DIF test strip presented a typical sigmoidal curve. In practice, the lower limit of detection using a strip reader was 0.5 ng/ml while 2 ng/ml by unaided visual assessment. Samples of milk were spiked at 2–8 ng/mL, presenting recoveries between 94.5 and 107%, and the coefficient of variation (CV,%) (1.6–9%). The data above suggests that the strip meets the requirements of high sensitivity, good specificity, simplicity and speed, as well as the characteristics of reproducibility and accuracy.