Fabricating Periodic Sandwich SERS Structure in Detecting SARS-CoV-2 S Protein with High-Performance

This study reported a sandwich SERS structure in detecting SARS-CoV-2 spike protein (SARS-CoV-2 S protein) with high performance. The periodic Ag nanoarrays (AgNAs) functionalized with angiotensin-converting enzyme 2 (ACE2) were utilized as the bottom structure to specifically bound to the SARS-CoV-2 S protein. A complex of SARS-CoV-2 S protein antibody and 4-mercaptobenzoic acid (4-Mba) modified Au nanoparticles (AuNPs@4Mba@Antibody) were used as nanotags and top SERS enhancing structures. By utilized the "hot spots" in parallel and perpendicular directions, the SERS signals of the 4-Mba as reporters were largely enhanced. By modulated the diameters and the heights of the AgNAs, the SERS performance of the sandwich structures was optimized by using R6G as a stand analyst with limits of detection (LOD) of 1 x 10-9 M. By applied the optimized sandwich structures in detecting SARS-CoV-2 S protein in phosphate buffered saline (PBS) and pharyngeal swabs solution (PSS), the proposed sandwich structure illustrates a high performance, and the LODs were 0.1 fg mL-1 and 1 fg mL-1, respectively. This study presented an efficient way to construct a sandwich SERS structure in directly detecting SARS-CoV-2 S protein and this method illustrates a good potential in viral detection.