Nanostructure-Modified Optical Fiber Sensors for Detection of <i>Salmonella typhimurium</i> in Food

In this study, a nanostructure-modified bulge-tapered-bulge (BTB) optical fiber sensor was developed for the rapid and label-free detection of Salmonella typhimurium (S. typhimurium) in food samples. The BTB design improves the evanescent field interaction, and immobilized gold nanoparticles (AuNPs), copper sulfide nanoflowers (CuS-NFs), and nickel ferrite (NiFe2O4) cause localized surface plasmon resonance (LSPR), which amplifies the optical response to biomolecular interactions. The sensing surface was modified with S. typhimurium-specific antibodies that selectively recognize the antigen–antibody interactions. The fabricated sensor exhibited ultrahigh selectivity for nontarget bacteria, including Escherichia coli, Listeria monocytogenes, and Vibrio cholerae, and good stability against sodium dodecyl sulfate (SDS) treatment, pH variations, and environmental fluctuations in temperature and salinity. The detection range was −101–109 CFU/mL, and a low detection limit of 1 CFU/mL was achieved. These results demonstrate that the BTB fiber sensor has the potential for the sensitive, selective, and on-site detection of foodborne pathogens and can be used in the field of food safety.