Nanozyme-Energized SERS Sensor for Ultrasensitive Dual-Mode Bacterial Detection

Bacterial infections threaten public health security and impose an enormous medical and financial burden. Rapid, convenient, and ultrasensitive detection of pathogenic bacteria is critical for early diagnosis of bacterial infections. In this work, we develop an oxidase-like surface-enhanced Raman scattering (SERS) sandwich sensor consisting of capture and signal modules for ultrasensitive dual-mode bacterial detection. The bacterial species-identifiable aptamer-modified iron oxide nanoparticle-based capture module can achieve highly efficient bacterial enrichment in trace concentration. The signal module is prepared by loading plasmonic Au nanoparticles into oxidase-like mesoporous MnO2 nanozymes, followed by concanavalin A functionalization to form high-intensity SERS hotspots. We demonstrate that the signal module can adsorb SERS-inactive TMB molecules near the hotspots and oxidize them into SERS-active oxTMB, achieving significant amplification of the SERS signal. Meanwhile, the color change from colorless TMB to blue oxTMB endows it with a colorimetric sensing capability. By assembling the signal and capture modules with bacteria, the constructed sandwich sensor exhibits ultrahigh dual-mode detection sensitivity (7 CFU/mL for SERS, and 30 CFU/mL for colorimetric) and selectivity toward model pathogenic bacteria of Staphylococcus aureus. Moreover, the sensor enables rapid and accurate bacterial detection in sepsis blood samples, revealing its great potential for early diagnosis of bacterial infections in clinical settings.