Raman analysis of saliva from OSA patients: biophotonic-based point-of-care for disease monitoring and management.

Aim of our study is to validate a new biophotonic-based method to identify biomolecular markers present within saliva, that can be a decision support tool to clinically phenotypize patients. The study takes avantage of Raman spectroscopy (RS), a vibrational spectroscopy technique that provides a spectrum, which represents a biochemical fingerprint of the sample and can be used to discriminate OSA from control subjects (CTR). OSA patients (n=63) and heallthy NOT-OSA subjects (CTR, n=50) were recruited. Saliva was collected through a swab-Salivette® (SARSTEDT) and then it was centrifuged. The biofluid was analyzed with a Raman microspectroscope. Colorimetric and immunobased assays were also performed to quantify some of the molecules supposed to influence salivary signature after Raman data interpretation. The average Raman fingerprint obtained for the two groups, showed different peaks, that highlight significant differences in the molecular composition of saliva in OSA, compared to CTR. The interpretation of the spectrum and its comparison with reported databases, suggest that lactic acid can play a central role in the discrimination between OSA and CTR saliva, being prevalent in the spectrum of OSA patients. This observation was confirmed by the calculation of the spectral Area Under the Curve (AUC) and by colorimetric Lactate Assay. Our data demonstrate that saliva is an informative and easily access biofluid for OSA patients monitoring. Besides, the Raman Spectroscopy approach allowed us to make a step forward in the identification of a potential biomaker (the Raman spectrum), that could be used to monitor OSA patients and test therapy efficacy.