Development of a nanobody-horseradish peroxidase fusion-based competitive ELISA to rapidly and sensitively detect Enrofloxacin residues in animal-derived foods

The ability to reliably detect enrofloxacin in animal-derived food products has important health implications. In the present study, a nanobody-horseradish peroxidase fusion specific for ENR was generated to enable a sensitive and rapid competitive ELISA suitable for detecting enrofloxacin in samples of milk and animal tissue. An enrofloxacin hapten generated via the glutaraldehyde method was initially used to immunize an adult Bactrian camel as a means of constructing a phage library. Enrofloxacin−specific nanobodies were then selected through three rounds of biopanning, and HRP-fused versions of these nanobodies were then expressed. Lastly, these nanobodies were used to develop a sensitive cELISA for enrofloxacin detection in milk and animal tissues, with the resultant assay exhibiting an IC₅₀ of 37.41 ng/mL and a linear detection range (IC₂₀-IC₈₀) of 10.89 to 244.34 ng/mL. The limit of detection for this cELISA was 6.48 ng/mL, with 4.66 % cross-reactivity with ciprofloxacin, and recovery rates that ranged from84.99 % to 107.72 % together with an RSD below 10.70 %.