Rapid detection of Salmonella in milk by nuclear magnetic resonance based on membrane filtration superparamagnetic nanobiosensor

Establishing an efficient and rapid detection method to monitor and control Salmonella is of great significance for ensuring food safety. Here we prepared a new time domain nuclear magnetic resonance (TD-NMR) biosensor based on superparamagnetic nanoparticle (SMN) with ultrasmall particle size and applied it for the detection of Salmonella in milk samples by TD-NMR. The free biotinylated antibody specifically binds to the Salmonella in the homogeneous system through the antigen-antibody interaction, and the biotinylated antibody-Salmonella is captured by streptomycin on the SA-modified SMN by specific binding to biotin. The probes that are attached to the Salmonella separated by membrane filtration for last NMR transverse magnetization time (T2) signal detection. The whole process can accurately detect Salmonella at levels as low as 104 cfu mL−1 in less than 2 h. This method holds promise as a powerful analytical tool that enables rapid, nondestructive testing and reconfigurable target bacteria detection. •The method overcomes the “hook effect” in NMR of microbial detection.•The method has the features of nondestructive testing and complex matrix testing.•The method can be used to detect Salmonella in milk and PBS simultaneously.•Membrane filtration can separate unbound-probe in homogeneous phase.•Free biotinylated-antibody has a more immune efficiency than immobilized-antibody.