CAREER: Additive Biomanufacturing an Engineered Stem Cell Microenvironment

添加生物制造是打印3D生物结构的过程，其中干细胞与生物材料连接。制造的一个关键挑战是建立对打印生物材料结构的控制，以防止干细胞分化。该学院早期职业发展(CALEAR)奖支持基础研究，为推进添加剂生物制造过程(远场熔体电旋写入)的控制提供所需的知识。研究结果将导致为再生医学生产工程组织结构，因此，将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，并扩大未被充分代表的群体对研究的参与。在远场熔融电旋写入过程中，聚合物材料从针头拉到集电板上，从针尖加工的聚合物构成带电纤维。针尖和板之间的温差被定义为温度梯度；它影响纤维变形(决定纤维直径)和纤维之间的静电斥力(通过多个纤维的相对排列，决定3D聚合物结构中的孔大小)。具有微尺度纤维直径和孔大小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。为了预测温度梯度对纤维变形和静电斥力的影响，将建立一个多物理模型(耦合聚合物流变学和静电学)。第二个目标是建立纤维变形和纤维直径之间的关系，以及静电斥力和孔径之间的关系。扫描电子显微镜将被用来测量电纺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大小对3D干细胞限制的影响。将开发一个基于几何的模型来预测受限的3D焦点黏附位置分布(电纺纤维和定植细胞之间的点接触)对干细胞功能的影响。实验将在电纺构建物上定植干细胞，并将使用原子力显微镜和荧光共聚焦显微镜测量焦点黏附分布。将进行干细胞表面标志物的免疫化学以确认干细胞的限制。

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.