School of Biomedical Engineering, McMaster University, Canada.
Biofabrication. 2019 Apr 2;11(3):035002. doi: 10.1088/1758-5090/ab0798.
Bioprinting is rapidly developing into a powerful tool in tissue engineering, for both organ printing and the development of in vitro models that can be used in drug discovery, toxicology and in vitro bioreactors. Nevertheless, the ability to create complex 3D culture systems with different types of cells and extracellular matrices integrated with perfusable channels has been a challenge. Here we develop an approach that combines the xurography of a scaffold material (cellulose) with extrusion printing of bioinks onto it, followed by assembly in a layer-by-layer fashion to create complex 3D culture systems that could be used as in vitro models of biological processes. This new method, termed ExCeL, can recapitulate the complexities of natural tissues with a proper 3D distribution of cells, extracellular matrices, and different molecules, while providing the whole structure with mechanical stability, and direct and easy access to the cells, even the ones that are positioned deep in the bulk of the structure, without the need to fix or section the samples. Briefly, the bioprinting of predefined patterns with a feature size of ∼1 mm has been made possible by treating paper with the hydrogel's crosslinker and printing cell-embedded hydrogel that will solidify immediately upon contact with the paper. These impregnated layers can be used as single layers or in a layer-by-layer approach by stacking them (here up to four layers) for applications such as cell migration and proliferation in 3D structures composed of collagen or alginate. Cells are generally sensitive to the amount of FBS in their culture media and we have shown how FBS amount will effect cell migration. By cutting the paper in certain patterns, printing hydrogel on the remaining parts of it, and stacking the paper in layers, features like embedded channels are formed that will provide cells will better mass transfer in thick structures. This technique provides biologists with a unique tool to perform sophisticated in vitro assays.
生物打印技术正在迅速发展成为组织工程领域的一种强大工具，可用于器官打印以及开发可用于药物发现、毒理学和体外生物反应器的体外模型。然而，能够创建具有不同类型细胞和细胞外基质的复杂 3D 培养系统，并集成可灌注通道，一直是一个挑战。在这里，我们开发了一种方法，该方法结合了支架材料（纤维素）的微影术和生物墨水在其上的挤出打印，然后以逐层组装的方式创建复杂的 3D 培养系统，可作为生物过程的体外模型。这种新方法称为 ExCeL，可以通过适当的 3D 细胞分布、细胞外基质和不同分子来重现天然组织的复杂性，同时为整个结构提供机械稳定性，并直接且易于接触细胞，即使是那些位于结构主体深处的细胞，而无需固定或切片样本。简而言之，通过用水凝胶的交联剂处理纸张并打印嵌入细胞的水凝胶，可以实现具有约 1mm 特征尺寸的预定图案的生物打印，该水凝胶在与纸张接触时会立即固化。这些浸渍层可单独使用，也可通过堆叠（此处最多可堆叠四层）来分层使用，例如用于在由胶原蛋白或藻酸盐组成的 3D 结构中进行细胞迁移和增殖的应用。细胞通常对其培养基中的 FBS 量很敏感，我们已经展示了 FBS 量如何影响细胞迁移。通过以特定模式切割纸张、在其余部分打印水凝胶并将纸张分层堆叠，可以形成嵌入式通道等特征，这将为细胞在厚结构中提供更好的传质。这项技术为生物学家提供了一种独特的工具，可以进行复杂的体外检测。
