Wisconsin Institute for Discovery, University of Wisconsin-Madison, Madison, WI 53706, USA; Department of Mechanical Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA.
Wisconsin Institute for Discovery, University of Wisconsin-Madison, Madison, WI 53706, USA; Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA.
Acta Biomater. 2019 Sep 1;95:258-268. doi: 10.1016/j.actbio.2019.04.050. Epub 2019 Apr 24.
In tissue engineering applications, sacrificial molding of hydrogel monoliths is a versatile technique for creating 3D molds to control tissue morphology. Previous sacrificial templates fabricated by serial processes such as solvent casting and thermal extrusion/fiber drawing can be used to effectively mold internal geometries within rapidly polymerizing, bulk curing hydrogels. However, they display poorer performance in controlling the geometry of diffusion limited, ionically cross-linked hydrogels, such as alginate. Here, we describe the use of poly(vinyl alcohol)-calcium salt templates (PVOH-Ca) fabricated by micro-injection molding, a parallel mass-production process, to conveniently cast internal geometries within both bulk curing hydrogels and ionically cross-linked alginate hydrogels. Calcium salt solubility was discovered to be a critical factor in optimizing the polymer composite's manufacturability, mechanical properties, and the quantity of calcium released upon template dissolution. Metrological and computed tomography (CT) analysis showed that the template's calcium release enables precise casting of microscale channel geometries within alginate hydrogels (6.4 ± 7.2% average error). Assembly of modular PVOH-Ca templates to mold 3D channel networks within alginate hydrogels is presented to demonstrate engineering scalability. Moreover, the platform is used to create hydrogel molds for engineering human embryonic stem cell (hESC)-derived neuroepithelial organoids of a microscale, biomimetic cylindrical morphology. Thus, injection molded PVOH-Ca templates facilitate customization of hydrogel sacrificial molding, which can be used to generate 3D hydrogels with complex internal microscale architecture for diverse tissue engineering applications. STATEMENT OF SIGNIFICANCE: Sacrificial molding of hydrogel monoliths is a versatile technique for creating 3D molds for tissue engineering applications. Previous sacrificial materials fabricated by serial processes have been used to effectively mold internal geometries within rapidly polymerizing, bulk curing hydrogels. However, they display poor performance in molding geometry within diffusion limited, ionically cross-linked hydrogels, e.g. alginate. We describe the use of poly(vinyl alcohol)-calcium salt templates (PVOH-Ca) fabricated by micro-injection molding, an unparalleled mass-production process, to conveniently cast internal geometries within both bulk curing hydrogels and ionically cross-linked alginate hydrogels. Calcium release from the PVOH-Ca templates enables precise sacrificial molding of alginate hydrogels and the process is biocompatible. Moreover, we demonstrate its use to engineer the morphology of hPSC-derived neuroepithelial organoids, and modular PVOH-Ca template designs can be assembled to enable scalable 3D customization of hydrogel internal architecture.
在组织工程应用中，水凝胶单体的牺牲模塑是一种用于创建 3D 模具以控制组织形态的通用技术。以前通过溶剂浇铸和热挤压/纤维拉伸等连续工艺制造的牺牲模板可有效模塑快速聚合、整体固化水凝胶内的内部几何形状。然而，它们在控制扩散受限的离子交联水凝胶（例如藻酸盐）的几何形状方面表现较差。在这里，我们描述了使用微注塑制造的聚（乙烯醇）-钙盐模板（PVOH-Ca）的用途，微注塑是一种并行的大规模生产工艺，可方便地在整体固化水凝胶和离子交联藻酸盐水凝胶内铸造内部几何形状。发现钙盐的溶解度是优化聚合物复合材料的可制造性、机械性能和模板溶解时释放的钙量的关键因素。计量和计算机断层扫描（CT）分析表明，模板的钙释放可实现藻酸盐水凝胶内微尺度通道几何形状的精确铸造（平均误差为 6.4±7.2%）。展示了组装模块化 PVOH-Ca 模板以在藻酸盐水凝胶内成型 3D 通道网络的方法，以证明工程的可扩展性。此外，该平台还用于为微尺度仿生圆柱形形态的工程人胚胎干细胞（hESC）衍生的神经上皮类器官制造水凝胶模具。因此，注塑成型的 PVOH-Ca 模板可方便地进行水凝胶牺牲模塑的定制，可用于生成具有复杂内部微尺度结构的 3D 水凝胶，用于各种组织工程应用。 意义声明：水凝胶单体的牺牲模塑是组织工程应用中创建 3D 模具的通用技术。以前通过连续工艺制造的牺牲材料已被用于有效地模塑快速聚合、整体固化水凝胶内的内部几何形状。然而，它们在模塑扩散受限的离子交联水凝胶（例如藻酸盐）内的几何形状方面表现不佳。我们描述了使用微注塑制造的聚（乙烯醇）-钙盐模板（PVOH-Ca）的用途，微注塑是一种无与伦比的大规模生产工艺，可方便地在整体固化水凝胶和离子交联藻酸盐水凝胶内铸造内部几何形状。PVOH-Ca 模板中的钙释放可实现藻酸盐水凝胶的精确牺牲模塑，并且该过程是生物相容的。此外，我们证明了它在工程 hPSC 衍生的神经上皮类器官形态中的用途，并且可以组装模块化的 PVOH-Ca 模板设计以实现水凝胶内部结构的可扩展 3D 定制。
