Synthesis of photoaffinity labeled activity-based protein profiling probe and production of natural TetR protein for immunoassay of tetracyclines in milk

In this study, a photoaffinity labeled activity-based protein profiling probe for tetracycline drugs was first synthesized that was used to capture a type of natural TetR protein from Escherichia coli. The TetR simultaneously recognized 10 tetracycline drugs. Then it was used as recognition reagent to develop a direct competitive chemiluminescence immunoassay for detection of the 10 drugs in milk. The IC50 values for these drugs were in the range of 0.084–0.32 ng/mL, and the limits of detection were in the range of 2.0–9.0 pg/mL. Their recoveries from the standards fortified blank milk samples were in the range of 68.4%-91.3%. After comparison, the natural TetR protein and the developed method showed better performances than the previous TetR proteins and the related immunoassays. Therefore, this method could be used as a practical tool for routine screening the residues of tetracycline drugs in milk. Furthermore, this type of probe could also be used to produce the receptors and develop different immunoassays for other classes of drugs.