An integrated litmus test platform for low-background detection and photothermal inactivation of Salmonella typhimurium via HCR-urease signal amplification.
Herein, we propose a novel "low-background" biosensing platform integrating magnetic separation and hybridization chain reaction (HCR) for signal amplification, enabling ratiometric colorimetric detection and visual observation of S. typhimurium. In the presence of S. typhimurium, specific aptamer recognition triggers the HCR to couple the urease-labeled DNA to the HCR reporting system, ultimately generating a ratiometric colorimetric response upon enrichment by Fe3O4@PDA@PEI and magnetic separation. The assay demonstrates excellent sensitivity, achieving a detection limit of 2.34 CFU mL-1. Simultaneously, the ratiometric sensor enables direct visual detection of S. typhimurium at concentrations as low as 103 CFU mL-1. Furthermore, leveraging the photothermal properties of Fe3O4@PDA@PEI under 808 nm NIR irradiation significantly reduced S. typhimurium viability, thereby minimizing the risk of secondary contamination. Recovery rates of 84.2%-115.3% in common spiked food samples containing S. typhimurium confirm its practicality. This integrated "detection and inactivation" strategy offers a proactive defense for food safety.