Real-time imaging of fibrin-bead networks under compression

Mechanical forces are an essential aspect of development and healthy tissue maintenance. While the response of tissues and biopolymer networks under shear has received much attention, we are not yet able to deduce the mechanical properties of tissue from the microstructure alone. An emerging in vitro model system for tissues are fibrin networks containing inert particle inclusions. These networks mimic the cell-loaded structure of the extracellular matrix (ECM) and recapitulate distinct mechanical behavior of tissues, such as an apparent bulk stiffening of the sample under uniaxial compression. Here, we develop a custom compression device that allows for real-time imaging of the local micro-structure in the fibrin-bead network. We map the emergence of a densified network compaction near the driving plate and observe poro-elastic network relaxations for sufficiently high compression rates. Our results indicate a predominate role of non-uniform network compaction in modeling the compression-stiffening behavior of fibrin-bead networks and tissues.