Vascularization of critical-sized craniomaxillofacial defects

项目摘要 缺乏适当的血管化导致治疗临界大小的颅颌面的最终失败 缺陷。巨大的缺陷阻碍了血液成分从周围渗透。 环境进入缺陷的内部，从而阻碍血管生成。在这种情况下，血管 血管内皮细胞生长因子(VEGF)是重建组织供氧最有效的因子。 虽然外用血管内皮生长因子是在临界大小的缺损中形成血管的关键手段，但其轻微的 不加控制的给药是有风险的，可能会导致肿瘤。因此，常规方法不能用于 血管内皮细胞生长因子的包裹和传递。在这项提议中，我们将开发一种新的芯片上传递血管内皮生长因子的方法 使用微流控平台，具有精确和持续的释放能力。我们新颖的设计使我们可以 以高度可控和可重复性的方式单分散粒子，为我们提供了细化- 调整颗粒的大小、微观结构、承载能力和释放速度，同时平衡pH和 维持血管内皮生长因子的生物活性。血管内皮生长因子的释放不仅要受到控制和持续，而且要高度 由于将加载了血管内皮生长因子的颗粒移动到不想要的区域是不利的 而且可能会有风险。因此，在另一种策略中，加载了血管内皮生长因子的颗粒将被固定在新的3D打印机上 专门为严重缺陷设计的脚手架。这种新型脚手架的设计(申请专利)是 灵感来自钢筋混凝土，其中钢筋嵌入到主体材料中，以增强 支架的力学性能(提高100-375倍)。换句话说，它是一种混合型支架， 两个组成部分：1)骨架钢筋：无孔、可缓慢生物降解的组成部分 支架的机械必需品，以及2)主体成分：多孔和可快速生物降解的成分 承接支架的生物必需品。尽管钢筋的机械强度是其特性 这使得脚手架适合于临界大小的缺陷，这是Rebar的另一个功能，这是它的缓慢之处 可降解性(6个月)，使该设计成为血管内皮生长因子传递目的的完美选择。螺纹钢将提供 我们有机会将载有血管内皮生长因子的颗粒固定在固体表面上，而不让颗粒移动 其他地方。固定化过程本身就是我们实验室开发的一种新方法，它可以牢固地附着在 颗粒到脚手架的钢筋上。负载血管内皮生长因子的支架将进行详细的体外分析和 生物反应器内的释放调节，可以模拟人体状况。血管内皮生长因子的版本简介将是 调整以达到目标值(每天每cm3支架1.2 ng/ml)，并进行全面的体外分析 将评估该构建物的成骨和血管生成特性。血管内皮生长因子负载支架的优化研究 将在新西兰白兔身上进行一项详细的活体研究，使用临界大小的牙槽骨缺损。这个 将对新骨形成和血管生成进行全面研究，以评估负载血管内皮生长因子的支架的功能 与不含血管内皮生长因子的支架相比，以及用目前的治疗方式治疗的缺陷。

Project Summary Lack of proper vascularization leads to the ultimate failure in treatment of critical-sized craniomaxillofacial defects. The large size of the defect obstructs penetration of blood components from the surrounding environment into the inner parts of the defect, and thus hinders vascularity. In such situations, vascular endothelial growth factor (VEGF) is the most effective factor that can reestablish the oxygen supply to tissues. While applying external VEGF is a key means for blood vessel formation in critical-sized defects, its slight uncontrolled administration is risky and can be tumorigenic. Thus, conventional methods cannot be used for encapsulation and delivery of VEGF. In this proposal, we will develop a new on-chip method for delivery of VEGF with precise and sustained release capabilities using a microfluidic platform. Our novel design allows making monodispersed particles in a highly controllable and reproducible manner, providing us with the ability to fine- tune the size, microstructure, loading capacity and release rate of particles, in addition to balancing the pH and maintaining the VEGF bioactivity. Release of VEGF must not be only controlled and sustained, but also highly localized in the region of the defect as moving the VEGF-loaded particles into unwanted areas is not favorable and can be risky. Thus, in another strategy, the VEGF-loaded particles will be immobilized onto a new 3D-printed scaffold specifically designed for critical-sized defects. The design of this novel scaffold (filed for patent) is inspired by reinforced concrete, in which reinforcing Rebars are embedded in the host material to enhance the mechanical properties of the scaffold (100-375 times improvement). In other words, it is a hybrid scaffold, made of two components: 1) Skeleton Rebars: non-porous and slowly-biodegradable constituent undertaking mechanical necessities of the scaffold, and 2) Host Component: porous and rapidly-biodegradable constituent undertaking biological necessities of the scaffold. Although the mechanical strength of Rebars is the property that makes the scaffold appropriate for critical-sized defects, another functionality of the Rebar, which is its slow degradability (6 months), makes the design a perfect choice for the VEGF delivery purpose. Rebars will provide us with the opportunity to immobilize VEGF-loaded particles on a solid surface and not let the particles move elsewhere. The immobilization process itself is a new method developed in our lab that can firmly attach these particles to the rebars of the scaffolds. The VEGF-loaded scaffold will undergo a detailed in vitro analysis and release adjustment inside a bioreactor, which can mimic the body condition. The VEGF release profiles will be adjusted to reach the target value (1.2 ng/ml per day per cm3 of scaffold), and the comprehensive in vitro analyses will evaluate the osteogenesis and angiogenesis characters of the construct. The optimized VEGF-loaded scaffold will undergo a detailed in vivo study using critical-sized alveolar bone defects in New Zealand white rabbits. The new bone formation and angiogenesis will be fully studied to assess the functionality of the VEGF-loaded scaffold in comparison with a VEGF-free scaffold, as well as defects treated with a current therapeutic modality.