CuO@SiO nanoparticle assisted click reaction-mediated magnetic relaxation biosensor for rapid detection of Salmonella in food.

Foodborne pathogens seriously threaten people's life and well-being. In this study, we developed a novel magnetic relaxation time (PCuMRS) biosensor by integrating phage, differential magnetic separation technology, and copper catalyzed click reaction to enable rapid and sensitive detection of viable Salmonella typhimurium (S. typhimurium) in food within 80 min. This assay utilized phage as the recognition element to accurately differentiate between viable and nonviable S. typhimurium. Initially, we prepared a complex of magnetic nanoparticles (MNPs) and phage to efficiently capture viable S. typhimurium. We synthesized CuO@SiO-phage nanoparticles loaded with numerous Cu ions to transform the concentration of S. typhimurium into a corresponding concentration of copper ions, which then modulate the click reaction between magnetic nanoparticles of varying sizes, leading to changes in both the number of small magnetic nanoparticles and magnetic signals. Based on this principle, we established a linear relationship (10-10 CFU/mL) between the concentration of S. typhimurium and the changes in magnetic signal, with a limit of quantification of 80 CFU/mL. Furthermore, the standard recovery rate and coefficient of variation of the sensor are 93.68%-100.36% and 0.59%-4.76%, respectively. The PCuMRS biosensor demonstrates outstanding sensitivity and a short detection time, making it a rapid, sensitive, and accurate method for identifying foodborne pathogens such as S. typhimurium, which has potential for applications in various other fields.