A novel low-field NMR biosensor based on dendritic superparamagnetic iron oxide nanoparticles for the rapid detection of Salmonella in milk

The growing threat of foodborne disease has made it imperative to develop rapid and efficient detection techniques. Here, we developed dendritic superparamagnetic iron oxide nanoparticles (SPIONs) combined with lowfield nuclear magnetic resonance (LF-NMR) biosensor for Salmonella detection in milk. We first used a Salmonella capture antibody and biotinylated detection antibody (BT-mAb) in the form of a sandwich in a 96-well plate to immobilize target bacteria. Then streptavidin modified polyamidoamine (SA-PAMAM) was used to connect BTmAb and functionally modified SPIONs. PAMAM-mediated SA amplified functionalized SPIONs via streptavidinbiotin amplification system, aggregated nanoparticles to form dendritic SPIONs, and achieved dual signal amplification. Finally, the dendritic SPIONs capture complex is eluted, and the lateral relaxation time T-2 of the water molecules around the SPIONs was used as the output of the target bacteria capture signal. The limit of detection of Salmonella in a buffer solution and milk was 2.6 x 10(4) CFU/mL, and the LF-NMR biosensor showed good specificity and anti-interference properties. Therefore, this innovative detection platform can be used as a sensitive, fast, and efficient tool for detecting foodborne pathogens.