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

ABSTRACT 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 10 3 to 10 1 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.