Abstract: In this study, a signal amplification enzyme-linked immunosorbent assay (AuNPs-HRP-IgG ic-ELISA) to detect enrofloxacin (ENR) in foods was established using gold nanoparticles (AuNPs) as a signal amplification carrier and horseradish peroxidase (HRP)-labeled secondary antibody as a signal probe. The detection limit (IC15) of this method for ENR was 5 × 10-4 ng/mL, the half maximal inhibitory concentration (IC50) was 0.24 ng/mL, and the detection range was 0.16–500 ng/mL. Compared with the traditional ELISA method (IC50 = 8.76 ng/mL), the sensitivity was significantly improved. The cross-reactivity of this method was less than 0.1% toward ciprofloxacin, ofloxacin, and norfloxacin, indicating good specificity. The feasibility of the AuNPs-HRP-IgG ic-ELISA was validated in terms of spiked recoveries in comparison with a commercial ELISA kit. The recoveries for spiked milk samples was 80.52%–102.66%, suggesting that this method could be suitable for the rapid and sensitive detection of ENR in actual milk samples. This study may also provide a new way to develop detection techniques for other related hazardous substances in foods.

Key words: enrofloxacin; gold nanoparticles; horseradish peroxidase; enzyme linked immunosorbent assay; sensitivity