面向小微器官修复的细胞三维直写组装技术研究

Capable of manufacturing live organs using cells and hydrogels, direct-write assembly of cells has demonstrated its superiorities and has become one of the frontier technologies in tissue engineering. It can also facilitate many fundamental and leading-the-edge researches in Biological and Medical sciences. However, the following key issues in this domain remain unsolved: 1. the size of the hydrogel strand is difficult to control in the extrusion of hydrogel solution; 2. the mechanical strength of the solidified hydrogel is low, resulting in poor shape fidelity; 3. it is difficult to precisely manufacture the details of small organs.. Based on the above analyses, the main research activities of this project are described below: 1. Investigation on the controlled extrusion of the hydrogel. The project will investigation the relationship between the process parameters and the size of the hydrogel strand. Based on this, the size of the hydrogel can be precisely controlled during the manufacturing process by the on-line tuning of the process parameters. 2. Compensation of the deformation of small organs. The project will analyze the deformation behavior of the solidified hydrogel and then utilize the predeformation technique to compensate the inevitable and large deformation of the soft hydrogel material. 3. Trajectory planning for the hydrogel plotting. It is difficult to manufacture small organs possessing very complicated cross-sections. The project aims to adjust the process parameters of the system while performing the direct write assembly. By doing this, the system’s capacities using different sizes of hydrogel strands are maximized to the full extent, such as the manufacturing productivity and details resolution. The efficiency and accuracy of the system can then be significantly improved.. In summary, the project will provide a new manipulation equipment for the frontier researches in Biological and Medical sciences in China.

细胞三维直写组装技术直接利用细胞与水凝胶在体外制造活体器官，是组织工程的前沿技术，为生物与医学领域提供先进的研究手段。这一领域存在的问题有：1、水凝胶在溶液状态下难以加工成型；2、水凝胶固化之后机械强度低、不易塑型；3、小微器官的细节特征难以精确加工。. 本项目的研究内容为：1、水凝胶的受控挤出成型方法，研究工艺参数与水凝胶条带尺寸的关系，在加工过程中在线调整工艺参数，精确控制水凝胶条带的尺寸；2、小微器官的变形补偿方法，研究固化后水凝胶的变形规律，利用反向预变形修正小微器官的轮廓，补偿其变形。3、水凝胶涂布轨迹规划，针对小微器官二维截面包含的复杂细节特征，提出水凝胶涂布轨迹与工艺参数协同规划的控制策略，充分利用系统在不同尺寸水凝胶条带下的加工能力与细节表现能力，在保证加工效率的情况下提高加工精度。. 本项目的研究将会为我国生物与医学领域的尖端科学研究提供新的操作仪器。

3D生物打印技术可以直接在体外打印出包含细胞的组织或器官，是一种有前景的器官体外培养手段。课题组以小微器官修复为目标，经过三年的项目研究，完成了项目的所有研究任务，简述如下：.(a)水凝胶受控挤出成型方法：本项目自主研制了气动注射系统，通过气压的高精度控制实现凝胶流量的受控挤出。在此基础上研究了工艺参数与水凝胶纤维直径的相互关系，实现了水凝胶纤维与空管直径的精确预测与控制。.(b)基于反向预变形的小微器官变形补偿方法：本项目通过实验研究发现，由于定型能力差，使用水凝胶打印的器官易在竖直方向上压缩。利用反向预变形的方法，在对打印器官切片时将其在高度方向上拉伸。实验结果表明，这种方法很好地补偿了器官的变形。.(c)复杂截面特征与工艺参数约束下的水凝胶涂布轨迹规划：3D生物打印追求器官的形状精度与器官内部的孔隙率。由于气动注射系统的起停时水凝胶流量的波动，因此，在进行涂布轨迹规划时应充分考虑器官的拓扑结构，减少打印轨迹的线段数量。对于复杂截面的器官，涂布轨迹应与器官的整体的轮廓相一致，对于薄壁类器官，涂布轨迹应仿形器官的截面轮廓。.(d)细胞三维直写组装系统的集成：本项目自主研制了高精度气动注射系统、3D生物打印机、设计了两种新型的水凝胶固化方法，并完成了上述各模块的系统集成，实现了很高的重复定位精度与气压控制精度。此外，该3D生物打印机的打印头可更换为激光测头，从而转换为高精度的非接触式三坐标测量仪。.(e)示范应用：本项目已经完成了包含细胞的水凝胶纤维制备与受损器官模型的修复两类示范应用。对于器官修复，课题组提出了一种基于生物器官截面轮廓曲线光滑连续的三维重建方法。. 本项目取得的研究成果：发表（或录用）学术论文8篇，其中SCI检索（或发表于SCI源刊）论文4篇，EI检索论文4篇；申请发明专利4篇；培养博士研究生3名，其中1人已毕业；培养硕士研究生5名，其中3人已毕业。

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