Research Center for Human Tissue and Organs Degeneration, Institute of Biomedicine and Biotechnology, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, People's Republic of China. These authors contributed equally.
Biofabrication. 2020 Jul 9;12(4):045003. doi: 10.1088/1758-5090/ab9906.
The development of exceptional bioinks with excellent printability, high fidelity, and excellent cell viability maintenance for extrusion bioprinting remains a major challenge. Gelatin is an ideal candidate bioink due to its biocompatibility, biodegradability, and non-immunogenicity. However, its inherently low viscosity and unstable physical gelation under physiological conditions make it unsuitable for direct extrusion bioprinting of tissue-like gelatin constructs with high fidelity. Herein, sequential chemical modification using reversible quadruple-hydrogen-bonded ureido-pyrimidinone (UPy) and enzyme-responsive tyramine moieties (Tyr) were devloped to endow the gelatin with a temperature-programmable viscosity and enzyme-controlled solidification, thus realizing enhanced printability and superior fidelity. As demonstrated in a proof-of-concept study, various cell-laden constructs were built based on our modified gelatin, including two-dimensional human bone marrow mesenchymal stem cell (hBMSC)-laden patterns, three-dimensional interconnected hBMSC-laden scaffolds, a reversible twisting-tension human-scale hBMSC-laden ear, a bicellular tibia-like construct containing hBMSCs and endothelial cells and a hexagonal prism-shaped hepatocyte-laden scaffold. The loaded cells in the construct have high viability of over 90% at 24 h, and show proliferation and protein secretion over one week, suggesting that Gel-UPy-Tyr-based constructs under physiological temperature not only can keep high fidelity, but also can support the growth and functions of the loaded cells.
开发具有出色打印性能、高保真度和出色细胞活力维持的特殊生物墨水，仍然是一个主要挑战。明胶由于其生物相容性、可生物降解性和非免疫原性，是一种理想的候选生物墨水。然而，其固有的低粘度和在生理条件下不稳定的物理凝胶化使其不适合直接挤出具有高保真度的类似组织的明胶结构。在此，通过使用可逆四重氢键脲嘧啶酮（UPy）和酶响应酪胺部分（Tyr）的顺序化学修饰，赋予明胶具有温度可编程的粘度和酶控制的固化，从而实现增强的打印性能和优异的保真度。在概念验证研究中，基于我们改性的明胶构建了各种细胞负载的构建体，包括二维人骨髓间充质干细胞（hBMSC）负载的图案、三维相互连接的 hBMSC 负载的支架、可逆扭转拉伸的人规模 hBMSC 负载的耳朵、包含 hBMSCs 和内皮细胞的双细胞胫骨样构建体以及六方棱柱形肝细胞负载的支架。构建体中负载的细胞在 24 小时时具有超过 90%的高活力，并且在一周以上时间内显示出增殖和蛋白质分泌，表明在生理温度下基于 Gel-UPy-Tyr 的构建体不仅可以保持高保真度，还可以支持负载细胞的生长和功能。
