Nuclear magnetic resonance biosensor based on streptavidin–biotin system and poly-l-lysine macromolecular targeted gadolinium probe for rapid detection of Salmonella in milk

Abstract

An accurate biosensor for rapid detection of Salmonella via low-field nuclear magnetic resonance (NMR) technology was developed. First, poly-l-lysine (PLL) containing several amino groups was modified with diethylene triamine pentacetate acid (DTPA) and gadolinium (Gd). The antibody was bound to Gd–DTPA–PLL through streptavidin and biotin interaction to obtain the probes. After the capture of Salmonella using the probes, the mixture was filtered to separate the excess probes. Finally, the filtrate was collected and measured by NMR. This method was successfully used in the simultaneous detection of Salmonella in pure culture and milk. The detection sensitivity was 2.4 × 104 cfu mL−1, and the overall detection process could be finished in 2 h. Because of the remarkable specificity of the probe and strong anti-interference, it was suitable for the direct detection of the complex matrix. The NMR biosensor has great potential to become a very promising biological molecular detection method.