High-resolution fabrication of porous microtubular scaffolds for vascular tissue engineering using two-photon stereolithography

Providing transport routes for oxygen and nutrient supply in macroscopic tissue remains a major challenge in tissue engineering. Among fabrication methods for perfusable microtubular structures, two-photon stereolithography (TPS) stands out due to its superior resolution, achieving features at the capillary scale. This study uses TPS to fabricate hollow tubes and investigates their feasibility as microtubular supply structures in in vitro tissue models. With optimized parameters, porous hollow tubes of different sizes (8 μm to 2 mm in diameter) with pore diameters of 1 to 50 μm were printed with the two photoresins IP-S and IP-Visio. IP-S demonstrated superior printability and higher shape accuracy compared to IP-Visio. IP-Visio prints were compatible with fluorescence microscopy, whereas IP-S exhibited high autofluorescence, which interfered with fluorescence imaging. The prints displayed partial wettability with similar contact angles between 71° and 76° on both flat and porous curved surfaces, with none of the liquids passing through the pores. Printed hollow tubes with pores were integrated into a perfusion system, and the permeability of molecules of 4, 70 and 150 kDa into the surrounding hydrogel matrix was assessed under physiological flow conditions. Structures printed with both photoresins facilitated the attachment and survival of primary human endothelial cells on top of flat prints (viability ≥97 %) as well as inside printed tubes. Finally, flat prints were tested in cytokine release experiments and provoked neither pro- nor anti-inflammatory responses of human macrophages and monocytes.