UC Irvine

How biological fibrous materials respond to forces and changes at the cellular scale is important for understanding what cells `feel' from their extracellular environment. The local mechanical property within a fibrin fiber network is dependent on the local structure of the network. Elastic force transmission through hydrogel depends on the arrangement of the fiber. A novel method for visualizing force transmission through this network is measuring the pixel fluctuation of individual fibers in the presence of an actively applied oscillation using embedded microbeads and optical tweezers. Optical tweezers can also be used for measuring local stiffness through active microrheology. After micropatterned crosslinking, fibrin hydrogels were shown to produce local stiffening directly and indirectly through strain hardening. This stiffening resulted in stiffness anisotropy and fiber alignment which MDA-231 cells were shown to respond to. Finally, a model of elastically connected nodes recapitulates some of the experimental observations such as fiber force transmission, strain hardening, and stiffness anisotropy when strained. Manipulating, measuring, and modelling of local stiffness changes in response to applied forces offers further insight into how cells sense their surroundings.