A colorimetric and SERS-based LFIA for sensitive and simultaneous detection of three stroke biomarkers: An ultra-fast and sensitive point-of-care testing platform

Stroke ranks as the second leading cause of disability and mortality globally. Biomarker detection represents a promising avenue for predicting disease severity and prognosis. The expression levels of metalloproteinase-9 (MMP-9), neuron-specific enolase (NSE), and N-terminal pro-brain natriuretic peptide (NT-pro BNP) in blood correlate with stroke severity. Hence, monitoring these biomarkers is crucial for stroke diagnosis and management. Point-of-care testing (POCT) offers on-site diagnostic capabilities, with lateral flow immunoassay (LFIA) being the most widely used method currently. However, traditional LFIA sensitivity requires enhancement. This study introduces an ultra-sensitive surface-enhanced Raman scattering-based lateral flow immunoassay (SERS-based LFIA) strip for simultaneous detection of the three stroke biomarkers using SERS immune tags. Bimetallic core-shell structured SERS immune tags leverage the advantages of two metals, ensuring stability and enhancing Raman signals through plasmon resonance. This development of a POCT based on SERS-based LFIA strips offers rapid, sensitive, and multiplex detection of stroke biomarkers. The limits of detection (LODs) for MMP-9, NSE, and NT-pro BNP were 0.00020 ng mL^-1, 0.00016 ng mL^-1, and 0.00012 ng mL^-1, respectively. Furthermore, enzyme-linked immunosorbent assay (ELISA) validated the accuracy of SERS-based LFIA. Clinical sample analysis demonstrated consistency between outcomes obtained by SERS-based LFIA and ELISA. Thus, SERS-based LFIA presents a novel POCT approach for stroke diagnosis.