Three-dimensional (3D) bioprinting is a technology to print materials (bioink) with cells into customized tissues for regeneration or organoids for drug screening applications. Herein, a series of biodegradable polyurethane (PU)-gelatin hydrogel with tunable mechanical properties and degradation rates were developed as the bioink. The PU-gelatin hydrogel demonstrated good printability in 24-31 °C and could print a complicated structure such as the nose-shaped construct. Due to the excellent shear thinning and fast strain recovery properties, the PU-gelatin hydrogel also had long working windows for bioprinting (over 24 h), stacking ability (up to 80 layers), and feasibility for high-resolution printing (through an 80 μm nozzle). The structure stability of the PU-gelatin hydrogel was maintained by two-stage double-network formation through Ca2+ chelation and thermal gelation at 37 °C without any toxic cross-linking reagent. The compressive modulus of printed PU-gelatin hydrogel constructs increased in about 3-fold by the treatment of CaCl2 solution for 15 min and enhanced further after incubation because of the thermal sensitivity of PU at 37 °C. Mesenchymal stem cells (MSCs) printed with the PU-gelatin hydrogel through the 80 μm nozzle showed good viability, high mobility, and ∼200% proliferation ratio (or an ∼300% proliferation ratio through a 200 μm nozzle) in 10 days. Furthermore, the MSC-laden PU-gelatin constructs containing small molecular drug Y27632 underwent chondrogenesis in 10 days. The novel series of PU-gelatin hydrogels with tunable modulus, long working window, convenient bioprinting process, and high-resolution printing possibilities may serve as new bioink for 3D bioprinting of various tissues.

中文翻译：

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具有可调模量的双网络聚氨酯-明胶水凝胶，用于高分辨率3D生物打印。

三维（3D）生物打印技术是一种将具有细胞的材料（生物墨水）打印到定制的组织中以进行再生的方法，或将类器官打印到药物筛选应用程序中的技术。本文中，开发了具有可调的机械性能和降解速率的一系列可生物降解的聚氨酯（PU）-明胶水凝胶作为生物墨水。PU-明胶水凝胶在24-31°C下显示出良好的可印刷性，并且可以印刷复杂的结构，例如鼻状构造。由于出色的剪切稀化和快速应变恢复特性，PU-明胶水凝胶还具有较长的生物印刷工作窗口（超过24小时），堆叠能力（最多80层）以及高分辨率印刷（通过80次印刷）的可行性。 μm喷嘴）。PU-明胶水凝胶的结构稳定性通过在不使用任何有毒交联剂的情况下通过Ca2 +螯合和在37°C下热凝胶化的两阶段双网络形成而得以维持。通过用CaCl2溶液处理15分钟，印刷的PU-明胶水凝胶结构的压缩模量增加了约3倍，并且由于PU在37℃下的热敏感性，在孵育后进一步提高了。通过80μm喷嘴用PU明胶水凝胶印刷的间充质干细胞（MSC）在10天内显示出良好的生存力，高迁移率和〜200％的增殖率（或通过200μm喷嘴的〜300％增殖率）。此外，载有小分子药物Y27632的带有MSC的PU-明胶构建体在10天内进行了软骨形成。具有可调模量的新型PU-明胶水凝胶系列