CAREER: Additive Biomanufacturing an Engineered Stem Cell Microenvironment

增材生物制造是打印3D活体结构的过程，其中干细胞与生物材料界面。一个关键的制造挑战是建立控制打印的生物材料结构，以防止干细胞分化。该学院早期职业发展（Career）奖支持基础研究，为推进添加剂生物制造过程（远场熔融电旋书写）的控制提供所需的知识。研究结果将导致生产用于再生医学的工程组织结构，从而影响卫生部门和美国生物制造部门的竞争力。该奖项还支持工程教育，将3D打印纳入本科课程，向高中生介绍先进制造，扩大代表性不足群体在研究中的参与。在远场熔融电自旋书写工艺中，将聚合物材料从针尖拉到集电极板，从针尖处加工的聚合物构成带电纤维。所述针尖与所述板之间的温差定义为温度梯度；它会影响纤维变形（决定纤维直径）和纤维之间的静电斥力（通过多根纤维的相对排列，决定3D聚合物结构中的孔隙大小）。具有微尺度纤维直径和孔径的结构可以促进干细胞的限制，以防止干细胞分化。第一个研究目标是了解温度梯度对纤维变形和纤维间静电斥力的影响。将建立一个多物理场模型（耦合聚合物流变学和静电学）来预测温度梯度对纤维变形和静电排斥的影响。第二个目标是建立纤维变形与纤维直径之间的关系，以及静电斥力与孔径之间的关系。扫描电子显微镜将用于测量静电纺丝结构中的平均纤维直径和孔径。第三个目标是了解纤维直径和孔径对3D干细胞约束的影响。将开发一个基于几何的模型来预测受限的三维黏附点分布（电纺丝纤维和定植细胞之间的点接触）对干细胞功能的影响。实验将进行干细胞在静电纺丝构建体上的定植，并使用原子力显微镜和荧光共聚焦显微镜测量焦点粘附分布。干细胞表面标记物的免疫化学将用于确认干细胞禁闭。

Additive biomanufacturing is the process of printing 3D living constructs where stem cells interface with biomaterials. A key manufacturing challenge is establishing control of the printed biomaterial constructs to prevent stem cell differentiation. This Faculty Early Career Development (CAREER) award supports fundamental research to provide needed knowledge for advancing the control of an additive biomanufacturing process (far-field melt electrospin writing). Research results will lead to producing engineered tissue constructs for regenerative medicine and, therefore, impact the health sector and competitiveness of the US biomanufacturing sector. This award also supports engineering education by integrating 3D printing into the undergraduate curriculum, introducing high school students to advanced manufacturing, and broadening participation of underrepresented groups in research.In a far-field melt electrospin writing process, a polymer material is drawn from a needle to a collector plate, and the processed polymer from the needle tip constitutes the charged fiber. The temperature differential between the needle tip and the plate is defined as temperature gradient; and it affects fiber deformation (that determines fiber diameter) and electrostatic repulsion between fibers (that, through relative alignment of multiple fibers, determines pore size in a 3D polymer construct). A construct with microscale fiber diameters and pore sizes can facilitate confinement of stem cells to prevent stem cells from differentiation. The first research objective is to understand effects of temperature gradient on fiber deformation and electrostatic repulsion between fibers. A multi-physics model (coupling polymer rheology and electrostatics) will be developed to predict effects of temperature gradient on fiber deformation and electrostatic repulsion. The second objective is to establish relationships between fiber deformation and fiber diameter, and between electrostatic repulsion and pore size. Scanning electron microscopy will be used to measure mean fiber diameter and pore size in an electrospun construct. The third objective is to understand effects of fiber diameter and pore size on 3D stem cell confinement. A geometrical-based model will be developed to predict effects of confined 3D focal adhesion site distribution (point contacts between electrospun fibers and colonized cells) on stem cell function. Experiments will be conducted to colonize stem cells on the electrospun constructs, and the focal adhesion distribution will be measured using atomic force microscopy and fluorescent confocal microscopy. Immunochemistry of stem cell surface markers will be conducted to confirm stem cell confinement.