Rapid detection of Salmonella in milk by labeling-free electrochemical immunosensor based on an Fe₃O₄-ionic...

Electrochemical sensors show distinct advantages over other types of sensors in the rapid detection of microorganisms. Here, we attempted to construct a label-free electrochemical immunosensor based on an Fe₃O₄-ionic liquid (IL)-modified electrode to rapidly detect Salmonella in milk. The excellent ionic conductivity of the IL facilitated sensor construction, and the large surface area of nano-Fe₃O₄ provided numerous sites for subsequent experiments. An antibody was fixed on the Fe₃O₄-IL complex with polyglutamic acid modification by a simple infusion method. The microstructure of the Fe₃O₄-IL composites was investigated by scanning electron microscopy, and the elements and structures of the composites were analyzed by energy dispersive X-ray and Fourier transform infrared spectroscopy. Under optimized experimental conditions, the detection range of the constructed sensor was 3.65 × 10²-3.65 × 10⁸ CFU mL^-1, and the LOD was 1.12 × 10² CFU mL^-1 (S/N = 3). In addition, the prepared electrochemical immunosensor is convenient for detecting foodborne pathogens because of its outstanding stability, good selectivity, and repeatability.