Ultrasensitive Detection of <i>Escherichia coli</i> O157: H7 in Fruit Juice by SERS Immuno-Sandwich Assay with IR-808-Embedded Au@SiO ₂ Nanotags

High Resolution Image Download MS PowerPoint Slide Escherichia coli ( E. coli ) O157:H7 is a major foodborne pathogen that frequently causes contamination outbreaks in fruit juices, threatening food safety and public health. Conventional detection methods suffer from long assay time, low specificity, severe matrix interference and insufficient trace detection capability. Herein, we developed a sandwich-type surface-enhanced Raman spectroscopy (SERS) immunosensor based on antibody-functionalized IR-808-embedded Au@SiO 2 core–shell nanoparticles for rapid and ultrasensitive detection of E. coli O157:H7 in fruit juices. The silica shell effectively protected internal IR-808, endowing the nanotags with excellent SERS signal stability and reproducibility. Under optimized conditions, the sensor achieved quantitative detection of E. coli O157:H7 in spiked juice samples within 20 min, with an ultralow limit of detection of 10 CFU/mL, as well as outstanding specificity and anti-interference performance. This work provides a reliable tool for rapid screening of foodborne pathogens in fruit juice products, which has broad application prospects in food safety assurance.