Flexible PEG-LifeAct Crosslinkers Tune Actin Network Structure and Mechanics in a Contour Length Dependent Manner

In vitro studies of actin filament networks dynamically crosslinked with binding proteins enable direct probing of cytoskeletal mechanics as well as inspire new adaptive materials design. However, the physiochemical properties of actin binding proteins are difficult to re-engineer, thus, impeding the generation of relationships between crosslinker molecular parameters, network structure, and mechanics. Tailoring crosslinker physiochemical properties through the engineering of bio-synthetic constructs composed of polymer backbones and known actin binding motifs would enable direct targeting of desired structure-property relationships. As a proof-of-concept, bio-synthetic crosslinkers composed of highly flexible polyethylene glycol (PEG) polymers functionalized with the actin binding peptide LifeAct, are shown using bulk rheology and fluorescence microscopy to modulate actin filament network structure and mechanics in a contour length dependent manner. Additionally, the studied bio-synthetic gels exhibit mechanical properties observed in natively crosslinked F-actin networks. The presented results encourage further exploration of peptide-polymer constructs as tunable biopolymer crosslinkers to interrogate and control biopolymer network properties.