Label-Free Detection of DNA Base Mutation and Hybridized DNA by an Electrostatically Modified 3D Plasmonic Array

Surface-enhanced Raman scattering (SERS) represents a promising avenue for DNA detection as it offers intrinsic chemical insights with high sensitivity compared to conventional methods. However, label-free and quantitative detection of unmodified DNA by SERS remains a major challenge in DNA analysis. To overcome this challenge, we propose a positively charged plasmonic nanosurface for DNA capture and quantitative analysis. Highly sensitive and uniform SERS enhancement was realized by a three-dimensional plasmonic array supporting well-designed hybrid plasmonic modes. Subsequently, the plasmonic array was modified with an electrostatically functionalized PDDA (poly(diene-dimethylammonium-chloride)) self-assembled monolayer in a single step. The effectiveness of the resulting PDDA-SERS substrate was demonstrated by the label-free and quantitative detection of base content and base mutation in hybridized DNA. The PDDA-SERS substrate provides a robust platform for SERS analysis not only of DNA but also of other electronegative analytes.