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-enhancedRaman spectroscopy (SERS)-based salivary sensor platform using carbonnanofiber surface-anchored bimetallic Nickel@Silver core-shellnanoparticles (Ni@Ag/CNFs) has been demonstrated as an effective pre-diagnosticscreening tool for lung cancer by monitoring the anomalous concentrationsof potential biomarkers such as salivary imidazole compounds. Ni@Ag/CNFshave been fabricated using electrospinning followed by a two-stepprocess consisting of a chemical reduction and transmetallation process.Structural and morphological characterization of the material usingX-ray diffraction (XRD), scanning electron microscopy (SEM), and transmissionelectron microscopy (TEM) analysis confirmed the successful formationof bimetallic Ni@Ag core-shell nanoparticles homogeneouslydistributed over the surface of the carbon nanofibers. The performanceevaluation of the Ni@Ag/CNFs-based SERS substrate toward the Ramanreporter molecule rhodamine 6G (R6G) showed excellent enhancementof 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 ashistidine, histamine, and urocanic acid within the clinically relevantrange (0.2-0.6 mM) in lung cancer diagnosis. The developedSERS-based salivary platform has the potential to be deployed as anon-invasive and cost-effective pre-diagnostic tool for early detectionand mass screening of lung cancer.