SERS-Based Lateral Flow Immunoassay Combined with Enzymatic Recombinase Amplification for Quantitative, High-Sensitive Detection of Influenza A Virus

Accurate and convenient diagnosis of the influenza virus is of critical importance to prevent the spread of flu infections and guide therapy and treatment. This work reports the fabrication of a sensitive and quantitative surface-enhanced Raman scattering (SERS)-based lateral flow (LF) strip combined with enzymatic recombinase amplification (ERA) for the highly effective detection of the influenza A virus. Gold-shell silica-core nanoraspberries (NRbs) were used in this SERS-LF strip as a SERS substrate. Practical and convenient detection was accomplished by naked-eye visualization, and highly sensitive quantitative detection was accomplished by monitoring the intensity of the distinct Raman peaks associated with the SERS tags. Under optimal conditions, the sensitivity of this ERA-SERS-LF strip for the DNA standard of the IAV matrix gene is 10⁵ copies/mL by naked-eye visualization, and the limit of detection (LOD) was estimated to be 2.63 × 10³ copies/mL by SERS detection, lowered by nearly 40 times compared with visual results due to the signal enhancement of the SERS tags. Besides, quantitative detection for the DNA standard of the IAV matrix gene was obtained with a wide linear range (2.63 × 10³ copies/mL to 10⁹ copies/mL). Pseudoviruses of IAV and other respiratory viruses could be successfully identified by using the fabricated ERA-SERS-LF strip. Overall, the findings of this study demonstrate the prospects of the use of the ERA-SERS-LF strip as an effective tool for point-of-care testing (POCT) detection of viruses by virtue of its portability, good sensitivity, quantitative detection ability, and outstanding specificity.