A Dual-Mode Aptamer-Based Lateral Flow Test Strip for Rapid Detection of Salmonella typhimurium Based on the Photothermal and Catalytic Effects of Fe₃O₄@Au Composite Nanomaterials

In this study, a novel dual-mode signal amplification aptamer-based test strip method that utilizes the photothermal effect and peroxidase-like activity of Fe₃O₄@Au composite nanomaterials was developed for the rapid detection of Salmonella typhimurium. Under optimal conditions, a visual detection limit of 10⁴ CFU/mL was achieved based on peroxidase-like catalytic coloration. By utilizing the photothermal effect of Fe₃O₄@Au, a quantitative standard curve was established by plotting the temperature change (ΔT) against bacterial concentration. A linear detection range from 10⁴ to 10⁸ CFU/mL was achieved, with a lowest detection limit of 3.02 × 10² CFU/mL. The method demonstrated high specificity for S. typhimurium, and showed no cross-reactivity with Salmonella Paratyphi B, Listeria monocytogenes, Escherichia coli O157:H7, or Staphylococcus aureus. Furthermore, the test strip exhibited satisfactory storage stability. It was successfully applied to detect S. typhimurium in real samples, including milk, chicken breast, and pork. The recovery rates ranged from 80.54% to 104.35%. With its advantages including rapidity, simplicity, and accuracy, this method can effectively detect S. typhimurium in complex food matrices. It represents a promising strategy for rapid on-site food safety screening.