Toward In Vitro Vascular Wall Models: Digital Light Processing of Acrylate-Endcapped Urethane-Based Polymers into Tubular Constructs

Digital light processing (DLP) is emerging as a powerful tool for fabricating tissue engineering (TE) scaffolds, particularly for vascular TE and the development of representative in vitro vascular wall models. For the latter, biomaterials should mimick the biological and mechanical properties of native blood vessels. To fabricate tubular constructs, the DLP-printing process is optimized by exploiting acrylate-endcapped urethane-based (AUP) polymers as the presence of the acrylate end groups render them suitable for DLP printing and desirable mechanical properties arise from the urethane segments. Four AUP variants are synthesized, exploring polyethylene glycol (PEG) and polypropylene glycol (PPG) backbones with varying acrylate functionalities (di-acrylate versus hexa-acrylate), namely UPEG2, UPEG6, UPPG2, and UPPG6. Tubular constructs with precise dimensions and morphology are fabricated. PPG-based AUP polymers exhibit superior computer-aided design/manufacturing (CAD/CAM) mimicry compared to PEG-based derivatives. Construct characterization reveals tunable mechanical properties, with elastic moduli ranging from 45 to 259 kPa, reaching values of the human blood vessels. In particular, UPPG6 shows a two-fold higher elastic modulus compared to UPPG2. All materials show excellent biocompatibility. Additionally, surface modification with gelatin-methacryloyl (GELMA) significantly enhances the cytocompatibility of UPPG2 scaffolds. This study demonstrates the feasibility of fabricating tubular constructs with tunable properties using DLP and AUP polymers.