Development of ELISA and immunochromatographic assay for the detection of neomycin

Background: Reliable analytical methods are required to monitor neomycin residue levels in the livestock products. In particular, a more simple and rapid detection method is required in the veterinary fields. Methods: Competitive direct ELISA and immunochromatographic assay were developed using monoclonal antibody to detect neomycin in the animal plasma and milk. Results: No cross-reactivity of the antibody was observed with other aminoglycosides based on competitive direct ELISA methods, indicating that the antibody is highly specific for neomycin. Based on the standard curves, the detection limits were determined to be 6.85 ng/ml in PBS, 3.61 ng/ml in plasma, and 2.73 ng/ml in milk, respectively. Recoveries of neomycin from spiked plasma and milk at levels of 50200 ng/ml ranged from 87% to 108%. Concentration of intramuscularly injected neomycin was successfully monitored in the rabbit plasma through competitive direct ELISA. Immunochromatographic method was also developed using colloidal gold-conjugated monoclonal antibody. Through this method, the detection limits were estimated to be about 10 ng/ml of neomycin in PBS, plasma, and milk. Conclusions: Immunochromatographic assay developed in this study is suitable for the simple screening of neomycin residues in the veterinary field. Observed positives can be confirmed using a more sensitive laboratory method such as competitive direct ELISA. (C) 2005 Elsevier B.V. All rights reserved.