Nanozyme-mediated multi-mode cascaded visual lateral flow assay platform of enrofloxacin based on truncated aptamer and one-pot isothermal amplification

The widespread use of enrofloxacin (ENR) in livestock farming raises serious concerns for human health due to its persistent residues in food. Thus, this study innovatively developed a cascade-amplified "turn-on" lateral flow assay (LFA) for the highly sensitive and visual detection of ENR. The high-affinity truncated aptamer (E22), initially obtained through molecular docking simulation, as the recognition element. By combining one-pot rolling circle amplification (RCA) and restriction endonuclease, the generated single-stranded DNA were captured by functionalized gold-platinum nano-urchin probes (APNCs-PolyA-DP). Based on the generated initial colorimetric (CM) signal, the CM-LFA enabled quantitative detection of ENR in the range of 0.1-1000 ng/mL, with a visual detection limit (vLOD) of 0.1 ng/mL. Then, the peroxidase-like activity of APNCs catalyzed the TMB chromogenic reaction to produce enhanced colorimetric (EC) signals. Furthermore, the synergistic near-infrared photothermal (PT) properties of the oxidation product (oxTMB) and APNCs were utilized to construct a specific temperature mode. By leveraging the dual properties of oxTMB, the EC-LFA and PT-LFA achieved a wider linear range (0.01-1000 ng/mL) and an ultralow vLOD of 0.01 ng/mL, showing a 10-fold improvement over the CM-LFA. The application of the LFA to milk samples yielded overall recovery rates, ranging from 93.9% to 105.1%. Thus, this approach provides robust technical support for point-of-care testing (POCT) platforms and shows broad application prospects in food safety monitoring.