SERS-Based Immunochromatographic Assay for Sensitive Detection of Escherichia coli O157:H7 Using a Novel WS2-AuDTNB Nanotag

<i>E. coli</i> O157:H7 contamination in food and the environment poses a serious threat to human health. Rapid and sensitive identification of foodborne pathogens remains challenging. Here, we prepared tungsten disulfide (WS₂)-Au nanocomposites coupled with the Raman signal molecule 5,5'-dithio-bis-(2-nitrobenzoic acid) (DTNB) and antibodies to replace the conventional colloidal gold nanoparticles and applied SERS-active nanotags in the SERS-ICA method for highly sensitive detection of <i>E. coli</i> O157:H7. The large surface area and numerous effective SERS hotspots of WS₂-Au nanotags provide superior SERS signals. Under optimized conditions, this ICA achieves the quantitative detection of <i>E. coli</i> O157:H7 in a broad linear range of 8 × 10²-8 × 10⁷ CFU/mL and at a low detection limit of 175 CFU/mL. In addition, the test strip indicates high specificity for <i>E. coli</i> O157:H7 identification, favorable reproducibility, and shows good accuracy in the detection of actual food samples, such as milk and pork. The proposed assay can be used for rapid qualitative and quantitative detection of <i>E. coli</i> O157:H7 and has great potential for field application.