NMR rapid detection of Salmonella in milk based on ultra-small iron oxide nanobiosensor

Abstract The monitoring and control of foodborne pathogenic microorganisms to protect food safety is of great significance. A biosensor based on superparamagnetic ultra-small iron oxide nanoparticles (USIO NPs) combined with membrane filtration and low field nuclear magnetic resonance (LF-NMR) for rapid detection of Salmonella is introduced. First, free biotin-capture-antibodies and biotin-detection-antibodies were specifically bound to different targets of Salmonella in milk samples. Then streptavidin-coated USIO NP probes were coupled with the biotinylated monoclonal antibody to capture Salmonella. Finally, polyethersulfone membrane filtration was performed on the final reaction system to remove unbound-probes, and the transverse magnetisation time (T2) of the filtrate was measured by NMR to indirectly reflect the content of the target substance retained on the filter membrane. This method shows high specificity and anti-interference to Salmonella, and the limit of detection (LOD) in pure culture and real samples was 2.3×103 cfu mL-1 within 150 min.