Foodborne pathogenic bacteria are microorganisms characterized by rapid reproduction, posing significant threats to food and environmental safety. Consequently, the development of rapid and accurate detection methods for these pathogens is highly crucial. In this study, a dual-mode in situ detection platform designed for bacterial analysis has been developed. The platform employs a phage-immobilized hydrogel stir bar to specifically capture target bacteria. This process alters the microenvironmental pH value of the stir bar and causes the color change of bromocresol purple that has been buried in the hydrogel. The color change can be observed with the naked eye through the transparent hydrogel, thus achieving the purpose of quickly screening for the positive samples. Additionally, the ZnO/ZIF embedded within the hydrogel will generate reactive oxygen species (ROS) under the light exposure. Through photodynamic action, the targeted live bacteria will be killed effectively, and ATP will be released intracellularly. In the presence of D-luciferin and luciferase, the ATP in the positive samples triggers a bioluminescence reaction, the intensity of which can be quantified using a hand-held ATP bioluminescence sensor. The mutual verification of these two detection modes confers high accuracy and sensitivity to the method. Furthermore, the approach eliminates the need for any large-scale instrumentation, enabling rapid on-site detection. Under optimal conditions, the detection range for target live bacteria spans from 103 to 109 CFU·mL-1 within 35 min. The limit of detection (LOD) for the colorimetric is 103 CFU·mL-1 and the limit of quantification (LOQ) for bioluminescence mode is 30 CFU·mL-1.
Cong Cao, Rong Feng, Zhenzhong Yu et al.· Analytical Chemistry· 0 citations
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.
Lun Luo, Renjie Zhou, Wenhai Wang et al.· Analytica Chimica Acta· 0 citations
