Determination of Tilmicosin by Fluorescence-Based Immunochromatography

ABSTRACT

Tilmicosin has been widely used in the dairy industry, but this compound is hazardous to human health. Therefore, it is urgent to develop a rapid, convenient, sensitive, cost-effective, and user-friendly method to determine tilmicosin. A fluorescent microsphere-based immunochromatographic assay was developed for this analyte. A 200-nm red fluorescent microspheres were selected to be the label, and the mass of the labeled antibody was 4.48 µg/mL. 1-Ethyl-3-(3-dimethylaminopropyl)-carbodiimide was used to catalyze carboxyl groups on the surface of the microspheres. The optimum reaction time between the antibodies and fluorescent microspheres was 30 min, and under these conditions, high coupling ratios and stable conjugations were obtained. The linear dynamic range of the developed protocol was from 0.02 to 2.10 µg/L. The half maximal inhibitory concentration was 0.19 µg/L. The recoveries were from 87 to 98% with a coefficient of variation less than 7.14%. In comparison with a colloidal gold immunochromatographic assay, the developed method offered a higher coupling rate, lower amounts of antibodies, and higher sensitivity. This approach is simple, sensitive, and suitable for on-site applications on farms for rapid screening.

KEYWORDS:

• Fluorescent microspheres
• immunochromatographic assay
• labeling
• tilmicosin

Acknowledgments

We thank all professors in our research group for providing selfless guidance.