Integrated SERS and photothermal dual-mode ultrasensitive immunochromatographic detection for influenza A based on PDA@Au nanoprobes.

A multifunctional polydopamine-gold (PDA@Au) core-shell nanoprobe has been synthesized that simultaneously enables surface-enhanced Raman scattering (SERS), photothermal conversion, and visual signal output within a single structure. Based on these features, we developed a dual-modal LFA platform for H1N1 antigens detection through two complementary readout modes. The SERS and photothermal modes achieved detection limits of 1.34 pg/mL and 1.03 pg/mL, corresponding to 746-fold and 971-fold improvements compared to commercial Au-based LFAs. The platform also exhibited excellent specificity against other common respiratory viruses and high batch-to-batch reproducibility across detection modes. Clinical validation on 90 throat swab specimens showed strong agreement with RT-PCR results. The PDA@Au-LFA demonstrated sensitivities of 98.5% (SERS), 97.0% (photothermal), and 93.9% (visual), along with consistently high specificity (95.8%). These results highlight the PDA@Au-based LFA as a high-performance diagnostic platform, featuring sensitive, specific, and reproducible multimodal detection enabled by the integration of a novel signal transduction material.