(396c) Flexible Crosslinker Size Impacts Linear and Non-Linear Actin Network Mechanics

Biopolymers have provided consistent inspiration for the design of biomimetic adaptive materials. For instance, in vitro studies of actin networks have yielded insights into the physical underpinnings of stress-stiffening and mechano-responsiveness in semi-flexible biopolymers. The macroscale mechanical phenomena of these networks are directly linked to the properties of the proteinaceous crosslinkers present. While experimental interrogations of native actin crosslinkers are instructive, the discontinuous variance in their physiochemical properties impedes the generation of concrete relationships between the molecular details and macroscale mechanical outcomes. Recently, bio-synthetic actin crosslinkers have been pursued to systematically probe these crosslinker dependent structure-property relationships. Herein, we generate bio-synthetic crosslinkers composed of polyethylene glycol (PEG) polymers end functionalized with the actin binding peptide, LifeAct. Using bulk rheology and fluorescence microscopy, we probe the impacts of flexible crosslinker size on network structure and mechanics via changes in PEG molecular weight. A strong dependence is found between crosslinking affinity, network modulus, and non-linear mechanics with crosslinker size. The presented results inform new routes to design fully synthetic actin mimetic materials for a range of materials applications.