Hierarchical tubular structures from biodegradable and bioactive PEG-modified PBS-DLS copolymers

Advanced manufacturing techniques for fabrication of tubular structures using biodegradable and biocompatible materials are crucial for the progress of tissue engineering. However, using 3D printing or electrospinning alone to fabricate multilayered tubular scaffolds that mimic the structural features of the tubular tissue (for example coronary artery) is not always sufficient and the selection of suitable biomaterials is still an important criterion. In order to address these challenges, first, we selected new segmented poly(butylene succinate-dilinoleic succinate) (PBS-DLS) copolymers of different segmental composition (70 wt% and 60 wt% of hard segments, respectively) which were modified with poly(ethylene glycol) (PEG). The effect of the segmental composition of copolymers on their enzymatic degradation, bioactivity, and cytotoxicity was investigated. All polymers showed a decrease in molecular weight (up to 40%) as determined by GPC, and mass loss up to 10% after 20 days of enzymatic degradation as measured by gravimetric analysis. Morphological study revealed the appearance of holes and cracks on the surface of polymers and changes in semi-crystalline spherulitic morphology. The in vitro bioactivity study showed precipitation of biomimetic Ca/P crystals of different stoichiometry depending from the segmental composition of polymers: more crystalline polymers (70 wt% of hard segments) favored tricalcium phosphate-like crystals formation while polymers of lower crystallinity (60 wt% of hard segments) were more favorable for hydroxyapatite precipitation. Further, all copolymers showed excellent cell viability in in vitro tests. Finally, we have successfully fabricated hierarchical tubular structures from new copolymers by combining electrospinning and 3D printing techniques. SEM analysis revealed micro- and nano-topography and excellent interconnectivity between distinct layers. Overall, this research confirm the suitability of these materials for potential medical applications.