Rapid Raman Fingerprinting Identification of <i>Listeria monocytogenes</i> via Immunomagnetic Enrichment Coupled with Droplet-Shrinkage-Assisted SERS

Rapid identification of <i>Listeria monocytogenes</i> (<i>L. monocytogenes</i>) is critical to preventing outbreaks of foodborne listeriosis. Conventional methods required immunoassay or nucleic acid sequence recognition for indirect/labeled detection or identification of <i>L. monocytogenes</i>, separately. Herein, a facile label-free fingerprinting method was developed for direct identification of <i>L. monocytogenes</i> using immunomagnetic enrichment coupled with droplet-shrinkage-assisted surface-enhanced Raman spectroscopy (SERS). Immunomagnetic beads were used for specific enrichment of <i>L. monocytogenes</i> 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 <i>L. monocytogenes</i> contamination in meat and meat products.