Raman microspectroscopy of oral mucosa: Exploring Raman mapping in experimental carcinogenesis

Oral cancers are major killers among the South Asian Nations primarily due to late detection. The biochemical variations during cancer progression especially in the early stages needs to be explored to further detection and treatment regimen. Diagnosis and treatment protocols are dependent on histopathology, which is time-consuming and requires high-degree of expertise. Optical techniques such as Raman spectroscopy present immense potential towards label-free objective optical biopsy methods and has been shown to identify healthy, premalignant, cancerous changes along with inflammatory conditions and cancer field-effects in vivo. Raman mapping of tissue-sections can provide molecular level changes in oral mucosa layers during malignant transformation. In the present study, we have undertaken mapping of healthy and carcinogen-treated tissues from Hamster buccal-pouch, the widely used experimental carcinogenesis model. Two parallel cryosections of 5 and 20 micron were obtained. The 5-micron sections were stained to obtain histopathological correlation while selected areas from the 20-micron sections were mapped (WITec-Alpha-300R, 50X objective, 532nm). Maps were constructed using WITec-Project-5.1 software. Spectra from the regions of interest were processed and subjected PCA-based linear discriminant analysis using Unscrambler software. Initial findings suggest several informative clusters in tissue sections and segregation of healthy and tumor spectra with high accuracy. Further studies with more samples will involve analysis of the clusters and detailed correlation with histopathology to understand biochemical and morphological variations to achieve optical biopsy.