Abstract:With the food safety problems caused by foodborne Listeria monocytogenes becoming increasingly widespread and severe, the development of rapid and sensitive methods for detecting the pathogen will have great significance in ensuring the protection of human health and reducing economic losses. Here, we describe the development of a hydrogen peroxide-mediated Au-Fe3O4 magnetic nanoprobe assembly strategy to construct a magnetic relaxation switching (MRS) immunosensor for the rapid detection of foodborne L. monocytogenes. Hydrogen peroxide reduces the silver ions to elemental silver atoms, which then deposit on the surface of the gold atoms in the probe. This causes the assembly of the dispersed Au-Fe3O4 probes into an aggregated state, leading to a change in the transverse relaxation time (T2). During the immunoreaction, the content of horseradish peroxidase (HRP)-conjugated antibody is determined using the concentration of L. monocytogenes. Consequently, the HRP content regulates the hydrogen peroxide concentration, which in turn regulates the degree of Au-Fe3O4 probe assembly. Thus, the resultant change in the T2 signal based on the degree of nanoprobe assembly enables the quantitative detection of L. monocytogenes. This method achieved a sensitivity of 50 CFU/mL, a linear range of 102~106 CFU/mL, and a recovery rate range of 79.4%~105.9% in the detection of L. monocytogenes. When used to quantify the pathogen in ham, the nanoprobe assay returned results that were highly consistent with those obtained using quantitative PCR. Given its high sensitivity and specificity, good stability, and ease of use, this Ag@Au-Fe3O4-MRS immunosensor should be a powerful tool for the rapid detection of foodborne pathogens.
