Rapid detection of Salmonella in milk with a nuclear magnetic resonance biosensor based on a streptavidin–biotin system and a polyamidoamine-dendrimer-targeted gadolinium probe

Rapid and sensitive detection technology is the key to preventing food-borne disease outbreaks. In this study, a low-field nuclear magnetic resonance (NMR) biosensor based on polyamidoamine dendrimers was prepared for the rapid detection of Salmonella in milk. The polyamidoamine dendrimer was biotinylated by amide reaction and chelated to diethylene triamine pentacetate acid and gadolinium to form magnetic complexes. The antibody and magnetic complexes were combined through a streptavidin-biotin system using streptavidin as an intermediate bridge to obtain the immunoprobe. Salmonella was captured by the immunoprobe via antigen-antibody interaction and then separated from the mixture by membrane filtration. Finally, the longitudinal relaxation signal of the filtrate was obtained by NMR. The biosensor had excellent anti-interference capability and could detect Salmonella within 1.5 h at a sensitivity of 103 cfu mL-1. This method based on NMR can realize detection in complex samples and has the potential to be a quick and nondestructive method for detecting target bacteria.