M13 Bacteriophage-Based Sandwich Assay for Salmonella Detection: A Dual-Signal Approach Combining Colorimetric and SERS Techniques

Herein, a dual-modal detection strategy for Salmonella using an engineered bifunctional M13 bacteriophage is presented. A Salmonella-specific binding peptide was fused to the pIII protein, while a streptavidin (SA)-binding nanotag was displayed on the pVIII protein. Taking advantage of the approximately 2700 copies of pVIII per phage, the addition of SA-HRP enabled massive enzymatic loading, which served as the key to generating both SERS and colorimetric signals in the presence of TMB substrate. Under optimized conditions (37 °C, ~1.5 h), the assay achieved limits of detection of 3.4 CFU/mL for the colorimetric mode and 2.7 CFU/mL for the SERS mode. The method exhibited excellent specificity and demonstrated satisfactory accuracy in complex matrices including Penaeus vannamei, beef, and peanuts, highlighting its strong potential for practical application in rapid food safety detection.