Title: Force propagation in biological fibrous networks
Abstract: The mechanical properties (i.e. stiffness) of the extracellular matrix (ECM) inside human bodies is important for development, wound healing, and normal tissue function. At the macroscopic scale, the ECM can be viewed as a homogeneous material. However, at the cellular scale, the fibrous, heterogeneous nature of collagen and fibrin play a large role in how force propagates through the ECM. Rheological measurements within hydrogels are in the kPa range, while measurements of individual fibers are in the MPa or GPa range. Additionally, non-linear elastic properties, structure arrangement, and unknown preloading of the fibrous network makes force transmission at the cellular scale difficult to predict. Here we propose the use of several imaging techniques to predict the force propagation within a reconstituted collagen I or fibrin gel. The first aim is to measure displacement propagation caused by induced force centers, which can be biological, chemical, piezo electric, or otherwise, tracked at the fiber level or with embedded silica microspheres. The second aim is to measure additional properties of the network, such as tension in the fibers and microrheological measurements around the embedded silica microspheres, in order to predict values measured in the first aim. A deeper understanding of how forces travel outside of the cell will provide biologists with the tools to design and interpret experiments studying how cells respond to forces in biological fibrous networks.