Clots reveal anomalous elastic behavior of fiber networks

Abstract

The mechanical properties of many soft natural and synthetic biological materials are relevant to their function. The emergence of these properties from the collective response of the structural components of the material to external stress as well as to intrinsic cell traction, remains poorly understood. Here, we examine the nonlinear elastic behavior of blood clots by combining microscopy and rheological measurements with an elastic network model that accounts for the stretching, bending, and buckling of constituent fibrin fibers. We show that the inhibition of fibrin crosslinking reduces fiber bending stiffness and introduces an atypical fiber buckling-induced softening regime at intermediate shear, before the well-characterized stiffening regime. We also show that crosslinking and platelet contraction significantly alter force propagation in the network in a strain-dependent manner. Our mechanics-based model, supported by experiments, provides a framework to understand the origins of characteristic and anomalous regimes of non-linear elastic response not only in blood clots, but also more generally in active biopolymer networks.