Fabrication and Use of Electroless Plated Polymer Surface-Enhanced Raman Spectroscopy Substrates for Viral Gene Detection

Abstract

Surface-enhanced Raman spectroscopy (SERS) substrates are prepared by electroless Ag metallization and vapor phase Au deposition on nanostructured poly(chloro-p-xylylene) (nanoPPX) templates. These substrates exhibit quasi-periodic nanomorphology inherited from the underlying nanoPPX template, resulting in highly reproducible SERS signal (<10% spot-to-spot and substrate-to-substrate signal variation for Au/nanoPPX comprising contributions from substrate imperfections). These substrates are therefore chosen for developing respiratory syncytial virus (RSV) gene detection that requires high sensitivity, stability, and reproducibility of the Raman signal. Metallized nanoPPX films show enhancement factors of ∼104 to 106 that strongly depend on the metallization route and can be optimized by controlling the metallization parameters. RSV gene detection is achieved by using a molecular probe (MP) consisting of a fluorescent moiety and a thiol linker for attachment to the SERS substrate. To detect multiple targets, MPs are designed in two colors (Hex and Cy5 dyes) utilizing a broad range of fluorophores. Our approach provides reproducible dual-mode detection (i.e., fluorescent and SERS) where the assay results generated by fluorescence and SERS are self-confirmatory and eliminate false positives.