Hydrolytic degradation and in vitro studies of poly(alkylene citrate)-based polyesters modified with glutathione

Materials currently used for vascular grafts are characterized by limited biocompatibility. Especially challenging is obtaining the degradable graft to regenerate a patient's native tissue. Poly(alkylene citrates) (PACs) are promising for soft tissue engineering applications; however, their degradation must follow a specific profile and must not result in the formation of any substances cytotoxic to the human body. The aim of this study was to evaluate the processes that occur throughout the hydrolytic degradation of PACs with a 2:3 M ratio of citric acid and diol, additionally modified with an antioxidant compound: glutathione (GSH). The samples were tested after various time intervals of incubation in an aqueous environment (up to 3 months), taking into account the influence of the type of diol used (1,6-hexanediol or 1,8-octanediol), the time of polymer cross-linking (4 or 10 days) and the presence of a different amount of GSH (0.4 or 0.8 wt%). Structural changes in the samples were monitored by means of swelling capacity, mass changes, hardness tests, mass spectrometry, and UV spectrofluorimetry. After 3 months of degradation, a higher weight loss was observed for the samples based on 1,6-hexanediol (>20 wt%) than those based on 1,8-octanediol (6-16 wt%). Based on the values obtained, the approximate time of 80% of the mass loss was calculated, which was higher for samples cross-linked for 10 days than 4 days. The samples based on 1,8-octanediol degraded slower than those of 1,6-hexanediol, but their degradation pattern was more linear and the amount of heavy ions present in the supernatant was negligible. In vitro studies on L929 fibroblasts did not show a cytotoxic effect of the materials tested. The study proved that GSH does not cause significant changes in the degradation profiles, sufficiently providing the fluorescence properties of the materials. Furthermore, any drastic changes in the material for up to 3 weeks followed by progressive degradation may support the tissue before the regeneration process begins.