Bacterial biomineralization-engineered Ag-Pt nanozyme for label-free and sensitive colorimetric detection of enrofloxacin in aquatic products.

The overuse of enrofloxacin (ENR) in aquaculture poses significant threats to ecological security and food safety, generating an urgent demand for instrument-free on-site detection. Herein, a Listeria-templated Ag-Pt bimetallic nanozyme (Listeria-Ag@Pt) was fabricated via a bacteria-templated in situ mineralization strategy. The intact bacterial template not only prevents nanoparticle aggregation to maximize peroxidase-like activity but also imparts inherent molecular recognition capability toward ENR without requiring antibodies or aptamers. The presence of ENR can enhance the catalytic efficiency of the nanozyme, significantly accelerating the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by H2O2 to produce blue oxTMB. Based on this target-enhanced chromogenic response, a colorimetric sensing platform was established, exhibiting a wide linear range of 0.0025-20 mg/L and a low limit of detection (LOD) of 0.8 ng/mL. The method afforded satisfactory recoveries of 92.7%-105% with relative standard deviations (RSDs) of 2.2%-7.3% in aquatic products. With advantages of cost-effectiveness, simplicity, and excellent anti-interference performance in complex matrices, this naked-eye detection strategy shows promising application prospect for on-site monitoring of ENR residues.