In situ Raman-analysis of supercritical carbon dioxide drying applied to acellular esophageal matrix

Supercritical (SC) carbon dioxide (CO2) drying has shown potential interest on the production of dry decellularized extracellular matrices for tissue engineering. This work explores the feasibility of Raman spectroscopy as in situ analysis for the SC-CO2 drying monitoring of a decellularized esophagus. Esophagus tissue was dried within an optical accessible high pressure CO2 dryer while the Raman signals of the wet tissue were excited at 785 nm. Two different experimental procedures were explored: i) single step process (SC-CO2 drying alone) and ii) two steps process (water exchange by ethanol followed by SC-CO2 drying). The quantification of the removal of water or ethanol from the tissue during the drying was obtained evaluating the variation of the Raman signal intensity ratio during time. The measurement of water or ethanol removal curves during the drying process can be easily/successfully exploited for the in situ monitoring of the drying process of a general matrix/tissue.