2D Film-Like Magnetic SERS Tag with Enhanced Capture and Detection Abilities for Immunochromatographic Diagnosis of Multiple Bacteria

Here, a multiplex surface-enhanced Raman scattering (SERS)–immunochromatography (ICA) platform is presented using a graphene oxide (GO)-based film-like magnetic tag (GFe–DAu–D/M) that effectively captures and detects multiple bacteria in complex specimens. The 2D GFe–DAu–D/M tag with universal bacterial capture ability is fabricated through the layer-by-layer assembly of one layer of small Fe₃O₄ nanoparticles (NPs) and two layers of 30 nm AuNPs with a 0.5 nm built-in nanogap on monolayer GO nanosheets followed by co-modification with 4-mercaptophenylboronic acid (MPBA) and 5,5′-dithiobis-(2-nitrobenzoic acid).The GFe–DAu–D/M enabled the rapid enrichment of multiple bacteria by MPBA and quantitative analysis of target bacteria on test lines by specific antibodies, thus achieving multiple signal amplification of magnetic enrichment effect and multilayer dense hotspots and eliminating matrix interference in real-world applications. The developed technology can directly and simultaneously diagnose three major pathogens (Staphylococcus aureus, Pseudomonas aeruginosa, and Salmonella typhimurium) with detection limits down to the level of 10 cells mL⁻¹. The good performance of the proposed method in the detection of real urinary tract infection specimens is also demonstrated, suggesting the great potential of the GFe–DAu–D/M–ICA platform for the highly sensitive monitoring of bacterial infections or contamination.