Plasmonic metasurface-enhanced Raman spectroscopy for label-free discrimination of human and murine noroviruses

Noroviruses are a leading cause of acute gastroenteritis worldwide, and their rapid and reliable detection remains a significant challenge for current diagnostic technologies. In this work, we present a plasmonic metasurface platform based on Y-shaped nanocavity arrays designed for label-free viral detection using surface-enhanced Raman spectroscopy (SERS). The nanostructured metasurface was fabricated using electron-beam lithography and engineered to support plasmonic resonances near the 785 nm excitation wavelength, enabling strong electromagnetic field localization and Raman signal enhancement. SERS measurements were performed on human norovirus (HNoV) and murine norovirus (MNV), producing distinct vibrational fingerprints associated with viral capsid biomolecules. Despite the structural similarity between both viruses, multivariate statistical analysis based on principal component analysis (PCA) enabled clear discrimination between their spectral signatures, with the first two principal components explaining more than 98% of the total variance captured. These results demonstrate that plasmonic metasurfaces combined with SERS fingerprinting and statistical analysis provide a powerful strategy for the label-free identification of closely related viral pathogens. The proposed platform highlights the potential of nanophotonic biosensors for rapid pathogen detection in biomedical diagnostics and environmental monitoring.