Thermal and vibrational biomarkers of porcine oral mucosa: Influence of localization on hydric organization and physical structure

The aim of this study was to develop an experimental protocol to determine specific and reproducible biomarkers of the oral mucosa using a combination of thermal and vibrational techniques. This works deals with the characterization of mandible and maxilla biopsies, 4 mm by diameter, from porcine mucosa in both the hydrated and lyophilized state. Thermogravimetric analysis was carried out to measure hydration level of these tissues and to define the onset of proteins degradation. By differential scanning calorimetry, thermal transitions of water and proteins were evidenced and used to quantify the hydric organization (unfreezable/freezable waters) and to evaluate collagen thermal stability (through denaturation parameters). To complete this protocol, Fourier transform infrared spectroscopy was also used to identify specific vibrational signatures of the main layers of oral mucosa. Total and freezable water amounts are significantly higher in maxilla, due to morphological differences at the macroscopic level, while unfreezable water amount is independent upon localization. Denaturation temperature (in peculiar the temperature corresponding to 50% of collagen denaturation) largely increases with dehydration. This temperature denaturation is also dependent upon localization whatever the hydration, possibly due to differences in cross-links or interactions with other proteins of oral mucosa. The acquisition of thermal and vibrational biomarkers of oral mucosa will contribute to a better knowledge of these soft tissues for further studies on aging.