Label-Free SERS Salivary Biosensor Based on Ni@Ag Core–Shell Nanoparticles Anchored on Carbon Nanofibers for Prediagnosis of Lung Cancer

A highly sensitive, non-invasive, label-free, surface-enhanced Raman spectroscopy (SERS)-based salivary sensor platform using carbon nanofiber surface-anchored bimetallic Nickel@Silver core–shell nanoparticles (Ni@Ag/CNFs) has been demonstrated as an effective pre-diagnostic screening tool for lung cancer by monitoring the anomalous concentrations of potential biomarkers such as salivary imidazole compounds. Ni@Ag/CNFs have been fabricated using electrospinning followed by a two-step process consisting of a chemical reduction and transmetallation process. Structural and morphological characterization of the material using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) analysis confirmed the successful formation of bimetallic Ni@Ag core–shell nanoparticles homogeneously distributed over the surface of the carbon nanofibers. The performance evaluation of the Ni@Ag/CNFs-based SERS substrate toward the Raman reporter molecule rhodamine 6G (R6G) showed excellent enhancement of the order of 10 7 and a detection limit of 10 –12 M, demonstrating its efficiency in analyzing real-time saliva samples, especially toward detection of salivary imidazole compounds such as histidine, histamine, and urocanic acid within the clinically relevant range (0.2–0.6 mM) in lung cancer diagnosis. The developed SERS-based salivary platform has the potential to be deployed as a non-invasive and cost-effective pre-diagnostic tool for early detection and mass screening of lung cancer.