A paper-based colorimetric assay for rapid detection of four macrolides in milk

We prepared a group-specific monoclonal antibody (Mab) that recognized the four macrolides, clarithromycin (CLA), erythromycin (ERY), roxithromycin (ROX) and azithromycin (AZI). The 50% inhibition concentration (IC50) values of CLA, ERY, ROX and AZI were 0.16, 0.52, 0.76, and 0.99 ng mL−1, respectively. Based on the Mab, a paper-based colorimetric assay was developed for rapid screening of CLA, ERY, ROX and AZI in milk samples. The assay displayed cutoff values of 2.5 ng mL−1, 5 ng mL−1, 5 ng mL−1, and 10 ng mL−1, respectively. For quantitative determination, the results were obtained using a strip scan reader, with limit of detection (LOD) values for CLA, ERY, ROX and AZI of 0.095, 0.085, 0.055 and 0.175 ng mL−1, respectively. These results suggest that the immunochromatographic assay is an ideal candidate for fast screening and quantitative analysis of CLA, ERY, ROX and AZI residues in milk.