Filtration-Based SERS With In Situ Gold Growth in Bacterial Microenvironment for Rapid Detection of Low-Level Bacteria.

Rapid bacterial detection and timely antimicrobial susceptibility assessment are essential for effective infection management, yet remain challenging under clinically relevant low-concentration conditions. Here, we present a filtration-based surface-enhanced Raman scattering (SERS) platform based on a microenvironment engineering strategy, in which plasmonic nanostructures are dynamically formed within the bacterial microenvironment. Using a gold nanostructured glass microfiber membrane, the platform enables large-volume sample processing through size-selective bacterial capture, followed by in situ gold growth that generates bacteria-centered plasmonic hotspots directly around bacterial cells. This architecture fundamentally overcomes the intrinsic hotspot-bacteria mismatch in conventional substrate-based SERS systems, enabling highly sensitive and selective detection while effectively suppressing nonspecific interference in complex biological matrices. To further address sampling limitations at low concentrations, a minimal pre-culture strategy was introduced to enhance bacterial surface occupancy, improving the detection limit from 103 to 101 CFU/mL. In addition, SERS signal intensity directly reflects bacterial viability, allowing rapid differentiation of antimicrobial responses and enabling susceptibility assessment within 2 h. By integrating physical enrichment with microenvironment-driven signal amplification, this platform simultaneously achieves low-level detection and rapid antimicrobial susceptibility testing within a single system. These results highlight its potential as a next-generation integrated diagnostic platform for clinical sample analysis.