Dual-modal biosensing platform: Integrating phage-hydrogel patch with bioluminescence and surface-enhanced Raman spectroscopy for rapid detection of trace levels of live and dead Salmonella enterica serovar typhimurium on food surface.

Abstract

Salmonella Typhimurium, a major cause of gastroenteritis, represents a serious global public health threat. Complicating risk assessment, health hazards primarily arise from live bacterial infections, while the quantification of dead bacteria is essential for assessing prior contamination and potential exposure to immunostimulatory components such as lipopolysaccharide. This work presents a dual-modal biosensing platform that integrates a bacteriophage-functionalized hydrogel patch with bioluminescence (BL) and surface-enhanced Raman scattering (SERS) for the rapid quantification of live and dead Salmonella enterica serovar Typhimurium (S. typhimurium) on food surfaces. The hydrogel patch, fabricated from a polydopamine-polyacrylamide double network embedded with specific phages and Au nanoparticles@Ag nanowires, serves as a SERS-active substrate and a specific capture matrix. The platform operates on a dual-signal mechanism: live bacteria generate an ATP bioluminescence (ATP-BL) signal proportional to their count, while total bacteria are quantified via a sandwich complex formed with Rhodamine 6G-labeled phages in the hydrogel patch, producing an intense SERS signal. Then, the dead bacterial count is derived by subtracting live counts from the total count. This strategy achieved impressive detection limits of 0.34 CFU/cm2 (SERS for total S. typhimurium) and 0.67 CFU/cm2 (BL for live S. typhimurium). The hydrogel patch requires minimal sample pretreatment and maintains excellent signal stability for over 80 days post-application in the dark at room temperature. This versatile platform represents a significant advancement in rapid foodborne pathogen detection and has potential applications in food safety and public health surveillance.