MOF-assisted colorimetric-photothermal dual-readout lateral flow assay for rapid detection of Salmonella typhimurium.

Background

Foodborne pathogens remain a major threat to public health and food safety, among which Salmonella typhimurium is a leading cause of bacterial foodborne illness. Conventional culture-, immunoassay-, and nucleic-acid-based methods are reliable but often require laboratory facilities, trained personnel, and relatively long processing times, limiting their use for rapid on-site screening. Lateral flow immunoassays are attractive for field detection but commonly suffer from limited sensitivity and subjective visual interpretation. This study addresses the need for a rapid, specific, and more sensitive on-site assay for S. typhimurium.

Results

We developed a phage-assisted colorimetric-photothermal dual-readout lateral flow immunoassay using zeolitic imidazolate framework-67-aggregated gold nanoparticles (ZIF-67@AuNPs) as signal probes. The ZIF-67 scaffold promoted dense AuNP assembly and aggregation-induced localized surface plasmon resonance coupling, resulting in broadened visible absorption around 650 nm and enhanced photothermal conversion. ZIF-67@AuNPs achieved a photothermal conversion efficiency of 45.7%, markedly higher than that of AuNPs alone (22.7%). Phage-based capture and antibody-functionalized ZIF-67@AuNPs enabled selective recognition of S. typhimurium on the test strip. In the colorimetric mode, the assay showed a linear range of 3 × 104-1 × 107 CFU/mL with a visual limit of detection (LOD) of 3.0 × 104 CFU/mL. In the photothermal mode, the linear range was 103-106 CFU/mL and the LOD improved to 0.997 × 103 CFU/mL, giving approximately 30-fold higher sensitivity.

Significance

AND NOVELTY This work introduces a MOF-assisted LFIA that integrates phage-based biorecognition with colorimetric screening and photothermal quantification in a single test strip. The strategy reduces reliance on subjective visual judgment while retaining operational simplicity. The platform provides a practical approach for rapid on-site detection of S. typhimurium and can be extended to other foodborne pathogens by changing the recognition elements.