Experimental Comparison of Thin Film Surfaces to Detect Oral Salivary Biomarkers by Surface-Enhanced Raman Spectroscopy

Six potential thin film candidates, Bi, Ti, Al2O3, Ag, Au, and C, were prepared on Si substrate to determine the most suitable ones to detect three known salivary biomarkers, L-Fucose, L-Proline, and N-acetylneuraminic acid from surface-enhanced Raman spectrum. In the two-phase study, 5 mg of each biomarker substance was first diluted into 1 ml of Millipore water and then into 1 ml of artificial saliva. Artificial saliva was used to ensure the molecular homogeneity of the samples. The normalized and smoothed spectra were area normalized, and cubic k-nearest neighbors’ confusion matrixes and F1-scores were computed, in both phases. The results show that laser-deposited Bi and Al2O3 thin films along with the typical Au and Ag are useful in detecting biomarkers from saliva. Compositional and microtextural modifications could further improve the performance of thin films.