Rapid Raman Fingerprinting Identification of Listeria monocytogenes via Immunomagnetic Enrichment Coupled with Droplet-Shrinkage-Assisted SERS.

Rapid identification of Listeria monocytogenes (L. monocytogenes) is critical to preventing outbreaks of foodborne listeriosis. Conventional methods required immunoassay or nucleic acid sequence recognition for indirect/labeled detection or identification of L. monocytogenes, separately. Herein, a facile label-free fingerprinting method was developed for direct identification of L. monocytogenes using immunomagnetic enrichment coupled with droplet-shrinkage-assisted surface-enhanced Raman spectroscopy (SERS). Immunomagnetic beads were used for specific enrichment of L. monocytogenes from the complex matrix. Silver nanoparticles were shrunk to bacterial cell surface, which excited bacterial Raman fingerprints under radiation. The enhanced Raman signal at 477 cm-1 was selected for quantification, and the limit of detection was 7 CFU/mL in real meat sample juice. The consistent results between the proposed method and the plate counting method demonstrated its applicability. High accuracy, speed, and sensitivity endowed this method with a great potential for monitoring L. monocytogenes contamination in meat and meat products.