New High Performance Bioinks for 3D Extrusion Bioprinting

3D生物打印已成为设计用于再生医学的结构复杂的活组织的首选方法，并作为癌症研究和药物开发的模型。3D生物打印从结构的计算机模型开始，然后由打印机使用生物墨水逐层重建，生物墨水由生物材料基质中支持的活细胞组成。这种方法极大地受益于打印机技术的改进，打印机越来越便宜，然而，为了使3D生物打印真正发挥其潜力，现在迫切需要对生物墨水进行重大改进。生物墨水必须是可打印的，并具有足够的机械性能，以在打印后保持其形状，从而使细胞沉积成获得结构复杂的3D打印组织所需的定义明确的高保真多层形状。它们还必须模拟天然细胞微环境，以确保所需的打印后细胞行为，例如细胞粘附，增殖和分化，如果打印的构建体要实现其预期应用，则需要这些行为。因此，可印刷性和仿生性对于3D打印的构造在其期望的应用中有用都是重要的。目前的水凝胶以仿生为代价来奖励可打印性，在3D生物打印中有很多工作是利用基于少数稳健和众所周知的基本水凝胶（例如明胶、透明质酸和藻酸盐）的经过试验和测试的生物墨水。尽管这些具有良好的可印刷性，但是它们对于细胞来说并不理想，因为它们不呈现许多细胞系所需的生物化学线索，以鼓励所需的印刷后细胞行为，这些行为是产生具有应用中所需的高水平复杂性的组织所需的。在这个项目中，我们将开发新的高性能生物油墨，同时呈现印刷性和仿生性。我们的生物墨水将基于荚膜抗原片段1（Caf 1），由工程细菌产生的>1000个蛋白质单体亚基组成的长（>1微米）薄聚合物。我们之前已经学会了将Caf1设计成天然细胞外基质的无与伦比的模拟物，我们实验室的初步工作表明Caf1水凝胶具有令人鼓舞的可印刷性。我们预计，我们的基于Caf1的生物墨水将显示出与常见生物墨水（如藻酸盐）相匹配的可打印性水平，并且我们将展示如何利用其上级仿生学来制备复杂的组织构建体，这些构建体无法使用常用的基于水凝胶的生物墨水制备。

3D Bioprinting has emerged as the approach of choice to engineer structurally complex living tissues for use in regenerative medicine and as models for cancer studies and drug development. 3D Bioprinting starts with a computer model of a structure, which is then recreated by the printer layer-by-layer using a bioink, which consists of live cells supported within a biomaterial matrix. The approach has benefited greatly from improvements in printer technology and printers are increasingly affordable, however, for 3D bioprinting to truly fulfil its potential, significant improvements to bioinks are now urgently required. Bioinks must be printable and possess sufficient mechanical properties to hold their shape after printing, allowing the deposition of the cells into well-defined high-fidelity multilayer shapes required to obtain structurally-complex 3D printed tissues. They must also mimic natural cellular microenvironments to ensure desired post-printing cell behaviours e.g. cell adhesion, proliferation and differentiation, which are required if the printed construct is to fulfil its intended application. Thus, BOTH printability and biomimicry are important for a 3D printed construct to be useful in its desired application. Current hydrogels prize printability at the expense of biomimicry, with much work in 3D bioprinting utilizing tried-and-tested bioinks based upon a handful of robust and well-known basic hydrogels e.g. gelatine, hyaluronic acid and alginate. Although these have good printability, they are not, however, ideal for cells as they do not present the biochemical cues required by many cell lines to encourage desired post-printing cell behaviours that are required to produce tissues with the high levels of complexity demanded in applications. In this project we will develop new high performance bioinks that present BOTH printability and biomimicry. We will base our bioink upon Capsular antigen fragment 1 (Caf1), long (>1 micrometre) thin polymers composed of >1000 protein monomer subunits that are produced by engineered bacteria. We have previously learned to engineer Caf1 to become an unrivalled mimic of natural extracellular matrix, and preliminary work from our lab indicates that Caf1 hydrogels possess encouraging levels of printability. We anticipate that our Caf1-based bioinks will display levels of printability which match those of common bioinks such as alginate, and we will show how its superior biomimicry can be harnessed to prepare complex tissue constructs which cannot be prepared using commonly used hydrogel-based bioinks.