In the last decade, three-dimensional (3D) extrusion bioprinting has been on the top trend for innovative technologies in the field of biomedical engineering. In particular, protein-based bioinks such as collagen, gelatin, silk fibroin, elastic, fibrin and protein complexes based on decellularized extracellular matrix (dECM) are receiving increasing attention. This current interest is the result of protein’s tunable properties, biocompatibility, environmentally friendly nature and possibility to provide cells with the adequate cues, mimicking the extracellular matrix’s function. In this review we describe the most relevant stages of the development of a protein-driven bioink. The most popular formulations, molecular weights and extraction methods are covered. The different crosslinking methods used in protein bioinks, the formulation with other polymeric systems or molecules of interest as well as the bioprinting settings are herein highlighted. The cell embedding procedures, the in vitro, in vivo, in situ studies and final applications are also discussed. Finally, we approach the development and optimization of bioinks from a sequential perspective, discussing the relevance of each parameter during the pre-processing, processing, and post-processing stages of technological development. Through this approach the present review expects to provide, in a sequential manner, helpful methodological guidelines for the development of novel bioinks.

中文翻译：

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用于 3D 打印的蛋白质驱动生物墨水的当前趋势

在过去十年中，三维 (3D) 挤出生物打印一直是生物医学工程领域创新技术的热门趋势。特别是，基于蛋白质的生物墨水，如胶原蛋白、明胶、丝素蛋白、弹性、纤维蛋白和基于脱细胞细胞外基质 (dECM) 的蛋白质复合物正受到越来越多的关注。目前的兴趣是蛋白质的可调特性、生物相容性、环境友好性和为细胞提供足够线索的可能性的结果，模拟细胞外基质的功能。在这篇综述中，我们描述了蛋白质驱动生物墨水发展的最相关阶段。涵盖了最流行的配方、分子量和提取方法。蛋白质生物墨水中使用的不同交联方法，本文重点介绍了具有其他聚合物系统或感兴趣分子的配方以及生物打印设置。还讨论了细胞嵌入程序、体外、体内、原位研究和最终应用。最后，我们从顺序的角度处理 bioinks 的开发和优化，讨论了每个参数在技术发展的预处理、处理和后处理阶段的相关性。通过这种方法，本综述有望以连续的方式为新型生物墨水的开发提供有用的方法学指南。我们从顺序的角度处理 bioinks 的开发和优化，讨论了每个参数在技术发展的预处理、处理和后处理阶段的相关性。通过这种方法，本综述有望以连续的方式为新型生物墨水的开发提供有用的方法学指南。我们从顺序的角度处理 bioinks 的开发和优化，讨论了每个参数在技术发展的预处理、处理和后处理阶段的相关性。通过这种方法，本综述有望以连续的方式为新型生物墨水的开发提供有用的方法学指南。