"Stick-and-Sense": a flexible paper SERS tape for rapid, selective and high - sensitivity food and water pathogen detection.

Rapid detection of foodborne pathogens is vital for public health, yet conventional methods for identifying Escherichia coli are slow, costly, and laboratory dependent. We present a simple paper-based SERS sensor fabricated by coating commercial adhesive tape with self-assembled gold nanoparticles. The platform enables label-free discrimination of E. coli, Enterococcus, and Citrobacter in water using their characteristic Raman fingerprints and principal component analysis, achieving a calculated E. coli detection limit of 26 CFU/mL. To operate in complex food matrices, the substrate was functionalized with an anti-E. coli antibody, enabling selective detection in commercial milk at concentrations as low as 25 CFU/mL, thereby experimentally validating the sensor performance in a real food matrix. Compared to existing flexible SERS substrates, our dual-mode approach combining label-free identification in aqueous media with targeted immunodetection in food offers competitive sensitivity, straightforward fabrication, and an enhancement factor of ≈107. These results highlight the potential of this paper-based SERS sensor as an accessible tool for rapid, on-site microbial monitoring in both water and food safety applications.