In situ tissue-engineered vascular grafts (TEVGs) based on resorbable synthetic scaffolds have the potential to overcome the limitations of prosthetic graft replacement and provide off-the-shelf availability. Despite massive efforts in investigating new materials, up to date no TEVG is clinically available. One of the most important challenges for successful regeneration is to balance the scaffold degradation and tissue formation. There is an increasing demand for tools to monitor these parameters simultaneously and at a spatial resolution, as most of the currently applied methods can either access polymer degradation or tissue regeneration.
Raman microspectroscopy allows to characterize a sample based on molecule-specific spectral fingerprints, which enables label-free evaluation and imaging of a sample. This study investigated the potential of Raman microspectroscopy as an in situ tool to monitor degradation kinetics and mechanisms of supramolecular polymers which are applied as degradable scaffolds in in situ tissue engineering. Raman imaging was applied on in vitro degraded polymers, investigating different polymer materials, subjected to oxidative and enzymatically induced degradation. Furthermore, the method was transferred to analyze in vivo degradation of tissue-engineered carotid grafts after 6 and 12 months in a sheep model.
Multivariate data analysis allowed to trace degradation and to compare the data from in vitro and in vivo degradation, indicating similar molecular observations in spectral signatures between implants and oxidative in vitro degradation. In vivo degradation appeared to be dominated by oxidative pathways. Furthermore, collagen remodeling at the implant interface was monitored simultaneously to the assessment of polymer degradation.
Our results demonstrate the sensitivity of Raman microspectroscopy and imaging to determine degradation stages and the assigned molecular changes non-destructively, encouraging future exploration of this techniques as a quality assessment tool to monitor in situ tissue engineering."