Nano Silver-Coated Porous Silicon-Based Surface-Enhanced Raman Spectroscopy Substrate for Low-Concentration Dengue NS1 Protein Detection

Detection of nonstructural protein 1 (NS1) in saliva is a potential solution to noninvasive, early dengue detection. However, NS1 in saliva detected using enzyme-linked immunosorbent assay reports only 64.7% sensitivity and is undetectable using rapid test kits even in acute cases. Exploiting surface-enhanced Raman spectroscopy (SERS) and silicon (Si) as a low-cost, abundant material, a nano silver-coated porous silicon SERS substrate was developed for the novel detection of low-concentration NS1. The conventional wet lab electrochemical method was used to fabricate the PSi template, whereas the drop deposition method was used to deposit the AgNP on the PSi. Using rhodamine as the Raman marker, an enhancement factor of 53 was obtained, with a 0.01-mg/mL limit of detection (LOD), which is not spectacularly impressive. However, surprisingly, the SERS substrate surface functionalized with the dengue antibody resulted in the visibility of several peaks related to NS1 up to 0.001 mg/mL. Advanced lithography methods can further lower the LOD and enhance the performance of the PSi-based SERS substrate. Moreover, PSi-based SERS substrate fabrication allows for mass production and low costs. The study successfully developed the SERS substrate for its intended novel application: to detect low-concentration NS1.