Low-temperature Extrusion of Waterborne Polyurethane - Polycaprolactone Composites For Multi-Material Bio-Printing of Engineered Elastic Cartilage.

Three-dimensional (3D) bio-printing of elastic cartilage tissues that are mechanically and structurally comparable to their native counterparts, while exhibiting favorable cellular behavior, is an unmet challenge. A practical solution for this problem is the multi-material bio-printing of thermoplastic polymers and cell-laden hydrogels using multiple nozzles. However, the processing of thermoplastic polymers requires high temperatures, which can damage hydrogel-encapsulated cells. In this study, we developed waterborne polyurethane (WPU) - polycaprolactone (PCL) composites to allow multi-material co-printing with cell-laden gelatin methacryloyl (GelMA) hydrogels. These composites could be extruded at low temperatures (50-60°C) and high speeds, thereby reducing heat/shear damage to the printed hydrogel-capsulated cells. Furthermore, their hydrophilic nature improved the cell behavior in vitro. More importantly, the bio-printed structures exhibited good stiffness and viscoelasticity compared to native elastic cartilage. In summary, our study demonstrated low-temperature multi-material bio-printing of WPU-PCL-based constructs with good mechanical properties, degradation time-frames, and cell viability, showcasing their potential in elastic cartilage bio-fabrication and regeneration to serve broad biomedical applications in the future. This article is protected by copyright. All rights reserved.