Electrochemically engineered plasmonic nanostructuring on universally captured bacterial surfaces for label-free and...

Infections caused by bacteria remain a persistent global concern, highlighting the pressing need for rapid and highly sensitive diagnostic tools. Here, we report a dual-strategy sensing system comprising a 4-mercaptophenylboronic acid (4-MPBA)-functionalized nanopillar Surface-Enhanced Raman Spectroscopy (SERS) substrate and an electrochemical SERS (EC-SERS) platform for label-free and ultrasensitive identification of bacterial pathogens. The 4-MPBA functionalization enables specific recognition of glycan moieties on bacterial cell walls, promoting surface enrichment of bacterial cells on the substrate within 2 h. Subsequent electrochemical gold deposition within 10 min generates uniform plasmonic hot spots directly on bacterial surfaces, effectively bridging the spatial mismatch between bacterial dimensions and SERS-active nanogaps. This approach enabled detection of diverse bacterial species at concentrations ranging from 1 to 100 CFU/mL, representing two to four orders of magnitude improvement over unmodified substrates. Furthermore, eight bacterial species were clearly differentiated using principal component analysis (PCA) and support vector classification (SVC). Taken together, the 4-MPBA-functionalized SERS substrate and EC-SERS platform represent a promising strategy for rapid, sensitive, and label-free identification of diverse bacterial species in complex biological environments.