Synergizing nanozyme-catalyzed signal amplification with magnetic separation for sensitive dual-mode Listeria...

A dual-mode biosensing platform for the sensitive detection of Listeria monocytogenes (L. monocytogenes) is presented. This method integrated vancomycin-modified magnetic nanoparticles (MNPs, 10‒30 nm) for efficient bacterial capture compared to L. monocytogenes monoclonal antibody, and aptamer-conjugated Fe-doped L-lysine-derived nanozyme (Fe@LS) for target recognition and signal amplification. The Fe@LS nanozyme exhibited pronounced peroxidase (POD)-like activity, catalyzing the oxidation of TMB with a Michaelis constant (K_m) of 0.63 mM and a maximum reaction velocity (V_max) of 1.89 × 10^-8 M·s^-1. Within this system, vancomycin-functionalized magnetic beads (Fe₃O₄@SiO₂@NH₂@van) enabled broad-spectrum binding to bacterial peptidoglycan, while the aptamer-modified Fe@LS (apt/Fe@LS) conferred the specific recognition of L. monocytogenes. Both fluorescence and colorimetric modes exhibited linear responses across a concentration range from 1.0 × 10² to 1.0 × 10⁸ CFU/mL (R² > 0.99), yielding a wider detection range compared to that catalyzed by horseradish peroxidase (HRP). When applied to simulated food samples (lake water, milk, and vegetable), the platform demonstrated satisfactory recoveries (90.0‒109.0%) and low inter-assay variability (< 8.0% RSD). The proposed dual-mode biosensing strategy offers a robust and reliable tool for the detection of L. monocytogenes in complex food environments.