New tool for fabrication of microtissues with anisotropic fibrous structure based on touch-spinning and 3D printing.

许多人体组织，如骨骼、肌肉、神经都是各向异性的。这种各向异性是由细胞外基质（ECM）的结构和胶原原纤维的取向提供的，它影响组织的力学性能和细胞的组织。然而，高分辨率的各向异性软组织3D打印是一项极具挑战性的任务。主要的挑战是将柔软的各向同性水凝胶基材料、细胞以及相对刚性的微纤维和纳米纤维结合起来，制造出类似于天然取向组织的各向异性结构。这个跨学科项目旨在解决这一挑战，并通过结合3D生物打印和现代纤维纺丝技术，开发制造各向异性组织的先进技术。我们的方法是基于触摸纺丝的集成，它允许纤维的精确沉积，到基于3D挤压的细胞负载水凝胶生物墨水的打印中。制备的纤维垫将用作打印水凝胶细胞生物墨水的衬底。多层各向异性结构将通过重复触摸纺丝和细胞印刷制造。由于纤维垫提供了机械稳定性，稀释的非粘性细胞封装水凝胶生物墨水可以通过窄喷嘴打印，而不需要施加高剪切力，从而获得更高的分辨率。纳米纤维垫也将作为细胞在水凝胶内形成定向结构的向导。触摸纺丝工艺的另一个优点是它不需要高电压，并且可以纺出各种聚合物纤维。此外，它可以用于将纤维沉积在细胞负载层上，而不依赖于聚合物的熔点。在这个项目中，我们将开发该技术并测试其用于骨骼肌微组织的制造。该项目的主要成果将是为各向异性组织的高分辨率制造开发全新的方法。这种方法有望成为制造不同类型的各向异性取向组织的有力工具。

Many human tissues such as bones, muscles, nerves are anisotropic. This anisotropy is provided by extracellular matrix (ECM) structure and orientation of collagen fibrils and it influences the mechanical properties of the tissues as well as organization of cells. 3D printing of anisotropic soft tissues with high resolution is, however, highly challenging task. The main challenge is to combine soft isotropic hydrogel-based materials, cells as well as relatively rigid micro- and nanofibers to fabricate anisotropic constructs similar to native oriented tissues. This interdisciplinary project aims to address this challenge and develop advanced technology for fabrication of anisotropic tissues by combining 3D bioprinting and modern fiber spinning technology.Our approach is based on integration of touch-spinning, which allows precise deposition of fibers, into 3D extrusion-based printing of cell laden hydrogel bioinks. Fabricated fibers mats will be used as substrate for printing of hydrogel-cell bioinks. Multilayer anisotropic constructs will be fabricated by repeating touch-spinning and cell printing. Since fibrous mats provide mechanical stability, diluted non-viscous cell encapsulated hydrogel bioinks can be printed through narrow nozzle without applying high shear force resulting in higher resolution. Nanofiber mats will also act as guidance for cells to form an oriented structure within the hydrogel. Another advantage of touch-spinning process is that it does not require high voltage and it allows spinning of various polymeric fibers. Moreover, it can be used to deposit the fibers on the cell-laden layer independently of the melting point of the polymer. In this project, we will develop the technology and test it for fabrication of skeletal muscle microtissues. The main output of the project will be development of radically new approach for high resolution fabrication of anisotropic tissues. This approach is expected to be a powerful tool for fabrication of different types of anisotropic oriented tissues.