Time-dependent response of bio-polymer networks regulated by catch and slip bond-like kinetics of cross-linkers

Although evidence has indicated that the presence of catch bond-like crosslinking proteins can significantly alter the viscoelastic response of bio-polymer networks, a detailed mechanistic understanding is still lacking. Here we report a computational investigation to examine how catch- or slip-bond kinetics of crosslinking molecules affects the time-dependent behavior of realistic F-actin and collagen networks. Specifically, it was found that, under oscillating shear, the rate of cross-linkers getting ruptured and then reformed reaches the maximum at intermediate driving frequency, eventually leading to a locally peaked bulk loss modulus of the network. Interestingly, when a pre-stress was applied the position of such peak shifted to higher frequencies for networks with slip bond cross-linkers. In comparison, the peaked loss modulus of actin network constructed by catch bond-like crosslinking molecules was reached at a lower driving frequency because of the stabilization effect of pre-stress on such cross-linkers. Similarly, the appearance of catch bond cross-linkers was also found to greatly alter the hysteresis of networks under staircase of sinusoidal shear excitations, all in good agreement with experimental observations. Finally, we showed that stress relaxation in slip-bond collagen networks becomes faster under increasing imposed strain, in direct contrast to networks constructed by catch bond crosslinking proteins where the characteristic timescale for stress decay grows with the strain. By elucidating the mechanism by which crosslink kinetics profoundly affects the bulk behavior of biopolymer networks, our study provides useful insights for the development of future biomaterials and understanding the physical role of cytoskeleton in various cellular processes.