A magnetic relaxation DNA biosensor for rapid detection of Listeria monocytogenes using phosphatase-mediated Mn(VII)/Mn(II) conversion

Abstract Listeria monocytogenes (L. monocytogenes), a psychrophilic and fatal foodborne zoonotic pathogen, with being one of the most common contaminants in foods, demands rapid and reliable detection techniques. Herein, we present a phosphatase (ALP)-mediated magnetic relaxation DNA biosensor enabling the rapid and sensitive analysis for L. monocytogenes in ham samples. The DNA probes were initially designed to specifically hybridize with targeted region of bacterial genomic DNA in L. monocytogenes, and the amount of ALP is related to the concentration of L. monocytogenes through DNA hybridization. Under enzyme-catalyzed reaction, ALP can induce Mn(VII) to convert into Mn(II). The valence state variation from Mn(VII) to Mn(II) results in a significant change of transverse relaxation time (T2) of surrounding water molecules, which can be used as an out-put of magnetic signal. Without any DNA amplification step, this magnetic biosensor could exhibit high sensitivity for L. monocytogenes detection with a linear range from 2 × 102 to 2 × 107 CFU mL−1, as well as a low detection limit (LOD) of 102 CFU mL−1. The constructed DNA biosensor, therefore, could offer an ideal candidate for the detection of food-borne pathogens with simple and reliable analytical performance.