Raman spectroscopic studies of oral cancers: correlation of spectral and biochemical markers

Both ex vivo and in vivo oral cancer studies performed using Raman spectroscopy over the past decade have demonstrated that the spectra of normal tissues are rich in lipids, while tumors have predominant protein features. However, in view of the variability in the Raman scattering cross section of biomolecules, it is pertinent to explore spectral features vis-a-vis biochemical composition in order to verify spectral markers as biochemical markers. Spectra of 20 pairs of normal and tumor oral tissues were acquired using a fiber optic probe coupled with a Raman spectrometer. The intensity associated with lipid (1440 cm(-1)) and protein (1450 and 1660 cm(-1)) bands were computed and correlated with the biochemical estimation for proteins, lipids, and phospholipids from the same tissues. The intensity of the lipid band was higher in normal tissues, while that of the protein band was higher in tumors. Biochemical estimation yielded similar results, i.e., high protein-to-lipid or -phospholipid ratio in tumors with respect to normal tissues. These differences were found to be statistically significant. Findings of curve-deconvolution and biochemical estimation correlate well and suggest that spectral features are the hallmark of underlying biochemical tissue composition.