An NMR immunosensor based on streptavidin-biotin signal amplification for rapid detection of Salmonella in milk

Sensitive and accurate detection of harmful pathogenic bacteria in food is of great significance to public health. In this paper, a nuclear magnetic resonance (NMR) sensor based on biological signal amplification was constructed. The carboxymethyl dextran (CMD) was used as both the probe skeleton and the chelating agent to realize the fast chelating adsorption of the signal source gadolinium ion. Finally, the magnetic complex and biotinylated antibody formed an immune probe through the biological bridge to achieve rapid capture of Salmonella . In addition, non-target bacteria such as Proteus vulgaris and Listeria monocytogenes were used to test the specificity of the constructed sensor. The sensor can detect Salmonella within 1.5 h under optimal conditions, the detection limit in milk is 7.4 × 10 3  CFU mL −1 , and the RSD (Relative standard deviation) of reproducibility experiment is 2.35%, which has good reproducibility.