Fabrication of a Low-Kink-Radius Bilayer Vascular Scaffold Incorporating a TPU Stent Fabricated via Melt Electrowriting and an Electrospun PCL/PU/gelatin Layer

This study investigates the fabrication of a small-diameter bilayer vascular graft, which is an inner layer fabricated from melt-electrowriting (MEW) thermoplastic polyurethane (TPU) scaffold and an outer co-electrospun layer made of heparinized polycaprolactone (PCL)/polyurethane (PU)/gelatin, aimed at mimicking the extracellular matrix (ECM). The bilayer structure exhibited good flexibility, mechanical stability, and anti-thrombogenic properties, overcoming the drawbacks of vascular grafts, such as high kink radius and tendency toward thrombosis. MTT assays proved cytocompatibility, showing an increase in cell proliferation over 7 days, the optical density of the bilayer vascular graft increased from 0.347±0.0065 on day 1 to 0.627±0.0055 on day 7, respectively, due to its fibrous structure and hydrophilic properties. Live/dead and SEM assays confirmed cell viability, attachment, and endothelial layer formation on the scaffold, which provides long-term graft patency. The bilayer graft with integrated MEW structure provided the balanced mechanical and kink-radius properties (ultimate tensile strength 7.09±0.16 MPa, Young’s modulus 22.78±0.91 MPa, suture retention 2.13 ± 0.09 N) with a low kink radius (9.14±0.10 mm), surpassing the mechanical properties of coronary artery. A heparin release profile of 70% after 4 weeks was obtained, thus increasing anticoagulant effects. This combination of synthetic (TPU, PCL, PU) and natural (gelatin) polymers yields a biocompatible, structurally stable vascular graft, which efficiently supports endothelialization, and thus has good potential for clinical vascular applications.