Understanding Mechano-Fibrinolysis: Fiber-Scale Multiphysics Experiments and Models

非技术总结：了解自然发生的生物材料是设计新的、更好的材料的关键一步，这些材料可以克服当今许多科学和健康挑战。其中一种生物材料是纤维蛋白，它是血凝块的重要组成部分。为了成功和安全地密封伤口，纤维蛋白已经发展成为一种高度可拉伸和有弹性的材料。同时，随着伤口逐渐愈合，纤维蛋白很容易去除。纤维蛋白的结构和化学成分之间复杂的、机械介导的相互作用使这些直径功能成为可能。在这个项目中，不同的显微镜技术将与计算模型结合使用，以更好地理解这种相互作用。该项目的知识也将直接适用于其他重要的纤维性生物材料，如胶原蛋白和弹性蛋白，以及它们的机械介导的结构-功能关系。在其科学范围之外，该项目的影响将被扩大，因为它通过为本科生和研究生创造研究机会，有助于培养未来的科学家。通过与非营利组织Science Mill的合作，它还将把有关纤维蛋白和其他纤维生物材料在人类健康和疾病中的作用的课程整合到非营利组织的夏令营课程中。通过这项工作，来自各行各业的幼儿园到九年级的学生，包括少数族裔背景的学生，将为健康、科学、技术、工程和数学领域的职业生涯做好更好的准备。技术概述：纤维蛋白是一种具有优异性能的半柔性生物聚合物。例如，纤维蛋白可以承受几百倍的变形而不会失效。它的可变形性和许多其他物理特性源于它跨越多个数量级的等级结构。因此，它是一种典型的生物聚合物，其研究将使人们对其他自然衍生和合成生物材料的基本理解成为可能，从而解决许多社会上最紧迫的问题。然而，关于纤维蛋白还有很多未知之处。在关于纤维蛋白和其他生物材料的未解之谜中，纤维蛋白的机械变形状态如何影响其酶解速率，即其机械裂解速率。这个问题是一个关键的问题，因为酶消化在许多重要的组织功能的调节中很重要，如组织生长和重塑，以及组织功能障碍，如癌症。在本研究中，这个问题将在纤维尺度上得到回答，即在单个纤维跨越的100纳米尺度上。为此，设计了一组基于原子力显微镜的实验，其中单个纤维蛋白纤维将变形，而它们在酶负荷下的消化将在显微镜下量化。这些实验将与详细的建模方法相结合，并整合到实验设计中。通过这种协同方法，将有可能描述机械变形对多种物理现象的影响，如酶运输、结合和酶活性，这些物理现象决定了纤维蛋白对酶消化的反应。为了确保这项研究揭示了机械的洞察力，而不仅仅是拟合观察结果，将在纤维网络尺度上验证机械纤维蛋白溶解的计算模型和理解，其中将预测负载纤维组装的降解并与实验进行比较。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Non-Technical Summary: Understanding naturally occurring, biological materials is a critical step toward designing new, better materials that can overcome many of today’s scientific and health challenges. One such biomaterial is fibrin, which is an important constituent of blood clot. To successfully and securely seal wounds, fibrin has evolved to be a highly stretchable and resilient material. At the same time, fibrin is easily removable as the wound is progressively healing. These diametrical functions are made possible by an intricate, mechanically-mediated interplay between fibrin’s structure and its chemistry. In this project, different microscopy techniques will be used in combination with computational models to better understand this interplay. The knowledge from this project will also have direct applicability to other prominent, fibrous biomaterials – such as collagen and elastin - and their mechanically-mediated structure-function relationships. Beyond its scientific scope, this project’s impact will be broadened as it contributes to the training of future scientists by creating research opportunities for undergraduate and graduate students. Through a collaboration with the non-profit Science Mill it will also integrate lessons about the role of fibrin - and other fibrous biomaterials - in human health and disease into the curriculum of the non-profit’s summer camps. As a result of this work, Kindergarten through grade 9 students from all walks of life including students with minoritized backgrounds will be better prepared for careers in health, science, technology, engineering, and mathematics.Technical Summary: Fibrin is a semi-flexible biopolymer with remarkable properties. For example, fibrin can undergo deformations of several hundred percent strain without failure. Its deformability and many other physical feats originate from its hierarchical architecture that spans many orders of magnitude. As such, it is a prototypical biopolymer whose study will enable fundamental understanding of other, nature-derived as well as synthetic biomaterials that can solve many of society’s most pressing problems. However, much remains unknown about fibrin. Among those unanswered questions about fibrin - and therefore about other biomaterials - is how fibrin’s state of mechanical deformation affects its rate of enzymatic digestion, i.e., its mechano-lysis. This question is a critical one to answer as enzymatic digestion is important in the regulation of many vital tissue functions such as tissue growth and remodeling as well as in tissue dysfunction such as in cancer. In this study, this question will be answered on the fiber scale, that is, on the 100s-of-nanometer-scale that a single fiber spans. To this end, a regiment of atomic force microscopy-based experiments was designed in which single fibrin fibers will be deformed, while their digestion under enzymatic loading will be microscopically quantified. These experiments will be combined with a detailed modeling approach that is integrated into the experimental design. Through this synergistic approach, it will be possible to delineate the effect of mechanical deformation on the multiple physical phenomena – such as enzyme transport, binding, and enzymatic activity – that determine fibrin’s response to enzymatic digestion. To ensure that this study reveals mechanistic insight rather than merely fitting observations, the computational model and understanding of mechano-fibrinolysis will be validated on the fiber network scale in which the degradation of an assembly of loaded fibers will be predicted and compared to experiments.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.