A Helper Antibody Based Competitive Fluorescence Immunochromatographic Assay for Quantitative Detection of Florfenicol in Poultry Eggs

Background Florfenicol (FF) is a chloramphenicol analogue used in animals, and florfenicol amine (FFA) is the main metabolite of FF. However, their residues in agricultural products are harmful to human health. A highly specific and sensitive assay for FF/FFA detection needs to be developed since the traditional detection methods are low in sensitivity. Objective In this study, a new method for rapid quantification of FF/FFA in poultry eggs by helper antibody-based fluorescent immunochromatographic assay (HAFIA) was established. Methods Triple antibodies including a primary monoclonal antibody (mAb) specific to the targets FF and FFA, a secondary polyclonal antibody (pAb) labeled with europium nanoparticles (EuNPs), and a helper monoclonal antibody (hAb), reacting with pAb but not with the mAb or the target antigen, are designed, which can form structural aggregation complexes in microwells with a single step of reactions. By loading the reaction sample solution, the triple-antibodies (mAb-pAb-hAb)-EuNPs complexes migrate to the test (T) line on the nitrocellulose membrane of testing strip and are competitively captured by the immobilized FF-bovine serum album (BSA) conjugates on the membrane and the FF/FFA targets in the sample solution. Results Fluorescence on the T line is read by a portable fluorescent strip reader in 10 min, and the result is given as the ratio of fluorescent intensities on the T and control (C) lines. This new fluorescent testing strip, with amplified signal from the triple-antibody complex, has 50-fold higher sensitivity than conventional colloidal gold-lateral flow immunoassays (CG-LFIAs), and can detect as low as 0.01 ng/mL FF and 0.1 ng/mL FFA targets from egg samples. Conclusion The developed competitive fluorescent immunochromatography method based on auxiliary antibodies has the advantages of high sensitivity and specificity for the rapid and quantitative detection of FF/FFA in poultry eggs.