The application of magnetic nanoprobes based on nuclear magnetic resonance (NMR) technology offers a rapid and highly sensitive approach for detecting foodborne pathogenic microorganisms. To enhance the detection efficiency of nuclear magnetic resonance technology for Salmonella and similar pathogenic microorganisms in food, a new detection method was proposed. Firstly, Bio-PEG-MNPs with high water solubility and biocompatibility were obtained by modifying magnetic nanoparticles with chain shaped polyethylene glycol and biotin. Secondly, by analyzing its particle size distribution through dynamic light scattering, a dual antibody sandwich NMR detection system for salmonella was optimized and constructed. Finally, the lateral relaxation time of salmonella was rapidly measured using low field NMR, with a focus on optimizing the key parameters of the detection system. The experiments revealed that Bio-PEG-MNPs had monodisperse and stable properties at MNPs/PEG of 1:15 and MNPs/Bio of 1:21. The experimental parameters for optimal detection of signals were a biotinylated antibody concentration of 1 µg/mL, incubation time of 60 min for both salmonella and probe, and SA dosage of 1 µg/mL. The NMR sensor was able to specifically detect salmonella in PBS with a lower limit of detection of 100 CFU/mL, including a wide range of detections from 102 to 107 CFU/mL. The sensor was effective in detecting salmonella in milk and pork samples in the range of 102 107 CFU/mL and CFU/g. This suggests that the NMR biosensor is a practical and accurate method for identifying salmonella in food. The technique can be used to identify salmonella in actual samples, which will encourage the use of low-field magnetic resonance imaging.
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