Mechanosensitive synthetic cell-regulatable hydrogels for tissue engineering

摘要 目前迫切需要工程化的功能组织来满足目前未得到满足的医学替代需求 或修复因疾病、损伤和先天缺陷而受损的组织和器官。生物材料 支架可以在工程组织中发挥关键作用，因为它们不仅提供机械支持和 提供生物活性分子和/或细胞，但它们也会降解，提供新的空间来支持细胞生长和 细胞外基质的产生。希望支架与新组织的速率相一致地降解 队形。支架的降解也会动态地影响其机械性能，这已被证明 调节宿主和移植细胞的行为，如扩散、增殖、迁移和分化。 尽管已经尝试预测和调整所使用的可生物降解的降解率 支架在植入之前用于特定的组织再生应用，目前很难控制其 植入后降解。以触发的方式调节支架的降解，外源或外部 已经使用了酶、pH和光等刺激。很少有人考虑将武力作为触发输入。 生物化学分子，如从宿主/移植细胞分泌的酶，已经有报道。 努力控制生物材料支架的降解率。然而，在以下方面仍然存在挑战： 以与支架降解匹配所需的速度和水平调节这些分子的产生量 具有工程化组织形成的轮廓，同时提供最小的机械支持损失。因此， 组织工程支架的力学响应对其降解的动态调节 环境可以允许智能生物材料的设计，当新形成的组织能够 支撑所需的载荷。创造机械敏感合成细胞(MSSCs)的合成生物学方法 具有机械敏感通道，用于模拟细胞动态分泌生物化学物质的能力 提出了生物材料支架对环境机械信号的响应。合成细胞是 细胞大小的脂双层囊泡包裹表达目的蛋白的无细胞表达系统。 将创建装载不同大小货物的MSSC，并使其能够在以下条件下释放有效载荷 将检查压应力(目标1)。然后将MSSCs封装在水凝胶系统中 检测外压缩应力介导的MSSCs有效载荷释放的调节能力 水凝胶降解(目标2)。最后，外压缩应力控制水凝胶的容量 将研究驱动水凝胶共包裹细胞功能的降解(目标3)。这项工作将 创造一种新型水凝胶，具有独特的机械响应机制，可动态反应 对他们的物理环境，预计将是有价值的工程广泛的组织。

Abstract There is great need for engineered functional tissues to address currently unmet medical need for replacement or restoration of damaged tissues and organs due to disease, injury and congenital defects. Biomaterial scaffolds can play a key role in engineering tissues because they not only provide mechanical support and deliver bioactive molecules and/or cells, but they also degrade to provide new space to support cell growth and extracellular matrix production. It is desirable for the scaffold to degrade in concert with the rate of new tissue formation. Scaffold degradation also dynamically affects its mechanical properties, which has been shown to regulate host and transplanted cell behaviors, such as spreading, proliferation, migration and differentiation. Although attempts have been made to predict and tailor the degradation rate of employed biodegradable scaffolds prior to implantation for specific tissue regeneration applications, it is currently difficult to control their degradation after implantation. To regulate scaffold degradation in a triggered fashion, exogenous or external stimuli, such as enzymes, pH, and light, have been employed. Few have considered forces as a trigger input. Biochemical molecules, such as enzymes secreted from hosted/transplanted cells, have already been reported in efforts to control the degradation rate of biomaterial scaffolds. However, there are still challenges regarding regulating the production amount of those molecules at a rate and level needed to match scaffold degradation profile with engineered tissue formation while providing a minimal loss in mechanical support. Therefore, dynamic regulation of the degradation of a tissue engineering scaffold via its response to its mechanical environment may allow for design of smart biomaterials that resorb as the newly formed tissue is able to support the required loads. A synthetic biology approach to create mechanosensitive synthetic cells (MSSCs) harboring mechanosensitive channels for mimicking the ability of cells to secrete biochemicals for dynamically degrading biomaterial scaffolds in response to environment mechanical signals is proposed. Synthetic cells are cell-sized lipid bilayer vesicles encapsulating cell-free expression system expressing proteins of interest. MSSCs loaded with different sized cargos will be created and their capability to release the payloads under compressive stress will be examined (Aim 1). The MSSCs will then be encapsulated in a hydrogel system for examining the capacity of external compressive stress-mediated payload release from MSSCs to regulate hydrogel degradation (Aim 2). Lastly, the capacity of external compressive stress-controlled hydrogel degradation in driving the function of hydrogel co-encapsulated cells will be examined (Aim 3). This work will create a new class of hydrogels with a distinct mechanism of mechanoresponsiveness that dynamically react to their physical environment and are anticipated to be valuable for engineering a wide range of tissues.