Cyclic Stiffness Photomodulation of Cell-Laden Protein-Polymer Hydrogels

Abstract

Although mechanical signals presented by the extracellular matrix are known to regulate many essential cell functions, the specific effects of these interactions, particularly in response to dynamic and heterogeneous cues, remain largely unknown. Here, we introduce a modular semisynthetic approach to create hydrogel biomaterials that undergo reversible stiffening in response to user-specified inputs. Employing a novel dual-chemoenzymatic modification strategy, we create fusion protein-based gel crosslinkers that exhibit stimuli-dependent intramolecular association. Linkers based on calmodulin yield calcium-sensitive materials, while those containing the photosensitive LOV2 (light, oxygen, and voltage sensing domain 2) protein give constructs whose moduli can be cycled with spatiotemporal control about living cells. We exploit these unique materials to demonstrate the significant role that cyclic mechanical loading plays on fibroblast-to-myofibroblast transdifferentiation. Our moduli-switchable materials should prove useful for studies in mechanobiology, providing new avenues to probe and direct matrix-driven changes in cell physiology.