Modular indirect labeling strategy enables universal and cost-efficient SERS immunochromatography for trace...

Pesticide residues pose serious risks to food safety, highlighting the need for rapid, sensitive, and cost-effective detection methods. We developed a modular indirect labeling surface-enhanced Raman scattering immunochromatography (SERS-ICA) that decouples the signal module from the recognition module. Au@Ag nanoparticles preloaded with 5,5'-dithiobis (2-nitrobenzoic acid) (DTNB) were conjugated with goat anti-mouse IgG to form a universal signal probe, onto which target-specific monoclonal antibodies were docked before use. This design avoids repeated probe synthesis and reduces antibody consumption by up to two orders of magnitude compared with direct labeling. After optimization of nanoparticle size, Ag shell thickness, reporter loading, and storage conditions, the system exhibited high signal stability. Using carbofuran as a model analyte, the SERS-ICA achieved a linear range of 0.0001-10 ng mL^-1 (R² = 0.985) and a detection limit of 0.51 pg mL^-1, with high specificity, reproducibility, and robust performance in spiked pear, carrot, and potato samples.