Sandwich fluorometric method for dual-role recognition of Listeria monocytogenes based on antibiotic-affinity strategy and fluorescence quenching effect

In this work, a sandwich fluorometric method for dual-role recognition of L. monocytogenes was developed based on antibiotic-affinity strategy and fluorescence quenching effect for sensitive and rapid detection of L. monocytogenes in ham samples. Vancomycin (Van) was conjugated with magnetic nanoparticles (MNPs) to recognize and capture target bacteria. Biotinylated aptamers were used to bind specifically to L. monocytogenes through the cell wall. The two agents recognized target bacteria at different binding sites showing satisfied specificity. The upconversion fluorescence response signal could be enlarged by using the inner filter effect (IFE) between the colored products produced by enzyme-catalyzing substrate and upconversion nanoparticles (UCNPs). The change in fluorescence intensity could represent the concentration of target bacteria over 102-2 × 108 CFU mL-1. The developed sandwich fluorimetric method achieved a low detection limit (LOD) of 2.8 × 102 CFU mL-1. Overall, the constructed fluorometric sensor could provide a simple and reliable method for the detection of L. monocytogenes.