Colorimetric-Catalytic-SERS Trimodal Immunochromatographic Assay for Multi-Scenario Monitoring of Gastrointestinal Infections

Direct pathogen detection in stool samples is the gold standard for diagnosing gastrointestinal infections, yet substantial technical challenges remain. Here, we report a versatile immunochromatographic assay (ICA) for simultaneous detection of both bacteria and virus, integrating a trimodal readout strategy combining magnetic enrichment with colorimetric, catalytic, and surface-enhanced Raman scattering (SERS) signals. We developed a self-assembled magnetic SERS nanozyme by electrostatically layer-by-layer depositing multilayer PtIr nanoparticles and Au nanostars onto a magnetic core, affording strong peroxidase-like activity and electromagnetic enhancement. In addition, a multi-feature fusion neural-network model was designed for intelligent SERS signal analysis, enabling accurate quantification of pathogen concentrations. The method exhibits high analytical performance across all three modalities: in colorimetric mode, the visual limits of detection (vLODs) were 5 × 103 CFU/mL for Escherichia coli O157 and 0.05 ng/mL for norovirus; in catalytic mode, a 2 min substrate-catalysis step reduced the colorimetric vLOD by 100-fold; in SERS mode, the detection limits were further lowered to 8 CFU/mL and 0.11 pg/mL via a quantitative algorithm. Application to 116 clinical stool samples showed detection rates consistent with quantitative real-time PCR, while reducing the assay time to 1/8. Therefore, this trimodal ICA holds strong potential for rapid and accurate detection of gastrointestinal infections across diverse scenarios.