Confocal Raman Micro-Spectroscopy for Discrimination of Glycerol Diffusivity in Ex Vivo Porcine Dura Mater

SIMPLE SUMMARY: Optical clearing is a promising method to overcome limitations in optical imaging technology for in-depth investigation. In this paper, 50% glycerol diffusivity in the framework of a passive diffusion model and water migration in ex vivo porcine dura mater was studied using confocal Raman micro-spectroscopy. Results show that glycerol concentration and diffusion coefficient vary at different depths, and collagen-related Raman band intensities were significantly increased for all depths after treatment. In addition, the changes in water content during optical clearing showed that 50% glycerol induces dehydration. Furthermore, these results could be translated to other fibrous biological tissues and organs. ABSTRACT: Dura mater (DM) is a connective tissue with dense collagen, which is a protective membrane surrounding the human brain. The optical clearing (OC) method was used to make DM more transparent, thereby allowing to increase in-depth investigation by confocal Raman micro-spectroscopy and estimate the diffusivity of 50% glycerol and water migration. Glycerol concentration was obtained, and the diffusion coefficient was calculated, which ranged from 9.6 × 10(−6) to 3.0 × 10(−5) cm(2)/s. Collagen-related Raman band intensities were significantly increased for all depths from 50 to 200 µm after treatment. In addition, the changes in water content during OC showed that 50% glycerol induces tissue dehydration. Weakly and strongly bound water types were found to be most concentrated, playing a major role in the glycerol-induced water flux and OC. Results show that OC is an efficient method for controlling the DM optical properties, thereby enhancing the in-depth probing for laser therapy and diagnostics of the brain. DM is a comparable to various collagen-containing tissues and organs, such as sclera of eyes and skin dermis.