生物3D打印是解决器官供需矛盾的有效方案，现阶段生物3D打印的瓶颈在于能否找到适合细胞共打印的理想 “生物墨水”。为研发用于器官再造的可细胞3D共打印的新型生物材料，本项目尝试从生物材料选择、生物正交反应的引入、干细胞3D共打印、活体移植四个方面进行设计，以达到基于生物材料和干细胞的脊髓损伤的有效修复。将以胶原蛋白和透明质酸为生物材料，分别以反应温和且高效的Cys/CBT和TCO/Tz两种生物正交反应体系构建可快速形成水凝胶的“生物墨水”，以装载有神经再生因子的明胶纳米粒控制因子的缓释，实现体外干细胞/“生物墨水”/再生因子的3D打印，形成可移植的神经支架。并构建大鼠全横断脊髓损伤模型，详细研究移植支架对脊髓损伤的修复效果。通过本项目的实施，有望探索出生物材料、成胶方式、再生因子、干细胞对损伤修复效果的影响规律，为研制出满足临床需求的脊髓损伤修复的创新性组织工程支架材料提供依据和奠定基础。

Currently, organ transplantation is the most effective way to cure end-stage organ diseases, but limited by severe shortage of donor organs. 3D bioprinting is a revolutionary technology for the fabrication of complex functional living tissues and organs due to its patient-specific design, high precision of geometrical structures and cellular distribution. However, current challenge of 3D bioprinting is the lack of ideal “bioinks” with great printability, biocompability and biodegradability. In order to develop the suitable system for 3D bioprinted tissues and organs, we plan to design and carry out this study in terms of the selection of biomaterials, the application of bioorthogonal reactions, cells-laden 3D bioprinting and living organ transplantation. Collagen (Col) and hyaluronic acid (HA) are the promising biomaterials for applications in biomedical field. Therefore, we choose them as the main structural materials in this study..Bioorthogonal reactions have rapidly attracted increasing interest, which occur specifically between functional groups and do not react with biological entities under physiological conditions. Among these reactions, a thiol-based bioorthogonal reaction between 2-cyanobenzothiazole (CBT) and cysteine (Cys), which happens in the firefly body with fast reaction kinetics, high efficiency and biocompatibility. In this study, collagen and HA are going to be used as main biomaterials and Cys/CBT-based bioorthogonal reaction pairs are separately modified onto Col/HA and used as crosslinker, and then the printable biomaterials are prepared. Moreover, the inverse electron-demand Diels–Alder addition reaction between Tz and TCO possesses a second-order rate constant of 10(3)-10(5) M−1 S−1, which is by far the fastest second-order rate constant among all these kinds of bioorthogonal reactions. This hydrogel system provides a suitable microenvironment for survival and proliferation of stem cells. In this study, we will aim to synthesize Col-TCO and HA-Tz, and use this hydrogel system to build 3D constructs through 3D bioprinting technology. .Spinal cord injury (SCI) is a life-shattering neurological disorder that often leads to permanent sensory and motor malfunction. Because neural stem cells (NSCs) can self-renew and differentiate into neurons, astrocytes, and oligodendrocytes, NSCs transplantation is considered to be a promising and an effective approach for the therapy of SCI, whereas challenges are the low survival of NSCs and glial cells differentiation of most NSCs under the injured spinal cord condition. Neurotrophic factors, such as brain derived neurotrophic factor (BDNF) and Neurotrophin-3 (NT-3), encourage the regrowth of severed axons, promote the differentiation of NSCs and are thought to be responsible for the survival of neurons. However, the quick degradation of neurotrophic factors is also a major problem. In this study, we demonstrate a controlled release system for neurotrophic factors based on gelatin nanoparticles as carriers. Gelatin nanoparticles are common delivery vehicles for numerous biomolecules in biomedical applications..In this study, we hope to provide ideal “bioinks” consisting of bioothorgonal group modified Col/HA, NSCs and neurotrophic factors-loading gelatin nanoparticles, which integrate the great biomaterials, bio-friendly crosslinking method for forming hydrogels, stem cells and controllable release carrier into one system, aiming to build living spinal cord scaffolds through 3D bioprinting technology. Thereafter, we are going to evaluate the recovery of the spinal cord injured animals by transplantation of 3D bioprinted living spinal cord scaffolds. Furthermore, the influence of biomaterials, crosslinking methods, growth factors and stem cells on spinal cord injury repair will also be analyzed. After above-mentioned studies, we hope to provide reliable and valuable basis for the clinical applications of innovative scaffolds for spinal cord injury repair.