Combining loop-mediated isothermal amplification and nanozyme-strip for ultrasensitive and rapid detection of viable Listeria monocytogenes cells and biofilms

Abstract

Foodborne diseases caused by Listeria monocytogenes (L. monocytogenes) occur frequently. The rapid, ultrasensitive, and visual methods are urgently needed for the detection of viable L. monocytogenes. We developed a novel lateral flow strip for visual and quantitative detection of viable L. monocytogenes cells and biofilms based on propidium monoazide-loop-mediated isothermal amplification (PMA-LAMP) and nanozyme. PMA-LAMP was used to identify viable L. monocytogenes, targeting hlyA gene by FITC- and BIO-modified primers in LAMP process. The optimized Fe3O4 nanoparticles with small size and good dispersibility combined with LAMP products of L. monocytogenes, which were captured by anti-FITC antibody modified on nanozyme strip under a suitable condition. This strip had features of stability, specificity, and visualization, which can also quantify L. monocytogenes with the detection limit of 10 CFU mL−1. Furthermore, the practicality of nanozyme strip had been proved in detecting biofilm formed by L. monocytogenes on stainless steel and lettuce surfaces.