Fe₃O₄@Au SERS tags-based lateral flow assay for simultaneous detection of serum amyloid A and C-reactive protein in unprocessed blood sample

Accurate detection of mutiple biomarkers in unprocessed blood via lateral flow immunoassay (LFA) strips remains challenging. Herein, we reported a novel surface-enhanced Raman scattering (SERS)-based LFA strip for ultrasensitive and simultaneous analysis of dual infection biomarkers by using functionalized Fe₃O₄@Au magnetic nanoparticles (MNPs). Antibody-modified Fe₃O₄@Au MNPs were designed as SERS nanotags and efficient enrichment tool. The target infection biomarkers were quickly captured and enriched from the blood sample by Fe₃O₄@Au nanotags. After washing to remove impurities, Fe₃O₄@Au nanotags acted as high-performance SERS reporters for quantitative detection of the target in the LFA strip. Through this strategy, the proposed Fe₃O₄@Au based LFA allowed quantified analysis of target infection biomarkers in unprocessed blood samples with the limits of detection of 0.1 ng/mL and 0.01 ng/mL for serum amyloid A (SAA) and C-reactive protein (CRP), respectively. By comparison, the proposed assay for SAA and CRP was 100-fold and 1000-fold more sensitive than standard colloidal gold strip by using the same antibodies, respectively. This magnetic SERS strip also exhibited excellent stability, specificity, and selectivity for complex samples and could be used as an effective tool for infectious disease diagnostics.