Rapid detection of fluoroquinolone residues in aquatic products based on a gold-labeled microwell immunochromatographic assay

Objectives Fluoroquinolones (FQs) are widely used in aquaculture, and their residues have caused many problems threatening human health. Here, this study aims to develop a colloidal gold immunochromatographic strip based on gold-labeled microwells to screen the residues of FQs on site.Materials and methods The Protein A Magarose Beads affinity chromatography method was adopted to purify the ascites against FQs. By using a strategy of heterologous coating antigen, different coating antigens are applied to detect FQs. The gold-labeled microwell immunochromatographic assay was used to improve the sensitivity of the test strip by the advanced reaction of antigen and antibody.Results The antibodies were verified to be of high purity up to 99%, and the titer reached 1:1 024 000. The combination (enoxacin-OVA and the antibody) detected the 4 banned FQs (pefloxacin, PEF; norfloxacin, NOR; lomefloxacin, LOM; ofloxacin, OFL) with the 50% inhibiting concentration (IC50) values ranging from 1.3 to 2.1 ng/mL and cross-reactions ranging from 67.3% to 106.1%. The analysis of spiked crucian carp, silver carp, grass carp, and shrimp samples showed that the limit of detection for PEF, NOR, LOM, and OFL was 4 mu g/kg. A comparative study with liquid chromatography tandem mass spectrometry (LC-MS/MS) demonstrated that the assay provided an effective screening tool for the rapid detection of FQs residues.Conclusions The results indicated that the test strip can realize full coverage recognition of the 4 banned FQs and has good accuracy, specificity, reproducibility, and stability; therefore, they are more suitable for rapid detection of FQs in aquatic products.