Fluorescent strip sensor for rapid and ultrasensitive determination of fluoroquinolones in fish and milk

The synthetic antibiotics fluoroquinolones are popular due to their good antibacterial performance and low price, but the risk to human health caused by their residues has attracted great attention. In this study, an ultra-sensitive mAb, 4D7, was prepared with an IC50 of 0.027 ng mL-1 to norfloxacin (NOR) and cross-reactivity of 19.7-47.7% to lomefloxacin (LOM), pefloxacin (PEF), ofloxacin (OFL), enrofloxacin (ENR), ciprofloxacin (CIP), and danofloxacin (DAN). Based on mAb 4D7 and Eu-fluorescent microspheres, a rapid and sensitive immunochromatographic strip was developed for the detection of fluoroquinolone residues in fish and milk. The detection ranges (IC20-IC80) of the strip for the detection of NOR, PEF, LOM, OFL, ENR, CIP and DAN were 0.19-1.1 μg kg-1, 0.39-2.1 μg kg-1, 0.5-2.6 μg kg-1, 0.43-3.3 μg kg-1, 0.61-3.5 μg kg-1, 0.69-5.5 μg kg-1, 0.52-3.4 μg kg-1 in fish, and 0.027-0.19 μg kg-1, 0.049-0.34 μg kg-1, 0.069-0.39 μg kg-1, 0.06-0.41 μg kg-1, 0.089-0.65 μg kg-1, 0.12-0.81 μg kg-1, 0.091-0.52 μg kg-1 in milk, respectively. The recovery rates in spiked sample tests were 88.6-113.6% with a coefficient of variation less than 8.4%. Thus the newly-developed strip was sensitive and reliable for rapid on-site detection of fluoroquinolone residues in fish and milk.