Cyclic Stiffness Modulation of Cell‐Laden Protein–Polymer Hydrogels in Response to User‐Specified Stimuli Including Light

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, a modular semisynthetic approach is introduced to create protein–polymer hydrogel biomaterials that undergo reversible stiffening in response to user‐specified inputs. Employing a novel dual‐chemoenzymatic modification strategy, fusion protein‐based gel crosslinkers are created that exhibit stimuli‐dependent intramolecular association. Linkers based on calmodulin yield calcium‐sensitive materials, while those containing the photosensitive light, oxygen, and voltage sensing domain 2 (LOV2) protein give phototunable constructs whose moduli can be cycled on demand with spatiotemporal control about living cells. These unique materials are exploited to demonstrate the significant role that cyclic mechanical loading plays on fibroblast‐to‐myofibroblast transdifferentiation in 3D space. The moduli‐switchable materials should prove useful for studies in mechanobiology, providing new avenues to probe and direct matrix‐driven changes in 4D cell physiology.

Visible Light‐Responsive Dynamic Biomaterials: Going Deeper and Triggering More

“…In preliminary work discussed previously, repeated stiffening and softening of hydrogel materials containing encapsulated 3T3 fibroblasts yielded differential activation as compared with statically stiff or soft materials. [ 55 ] Extension of this work in vivo would further elucidate the role of dynamic network stiffness on cell fate. [ 15,75 ]…”

“…Liu et al recently demonstrated reversible photoreversible stiffening of hydrogel biomaterials crosslinked with a diazide‐modified LOV2‐Jα fusion using SPAAC. [ 55 ] The conformation change of the LOV2‐Jα interaction is traceable by UV–vis spectroscopy, with 470 nm irradiation nearly bleaching the visible absorbance, which can be recovered over time in the dark (Figure 5C). Once formed, the hydrogel can be repeatedly softened and stiffened again over time with very brief 470 nm irradiation windows (Figure 5D); this process that can be cycled hundreds of times with no measurable hysteresis.…”

“…Once formed, the hydrogel can be repeatedly softened and stiffened again over time with very brief 470 nm irradiation windows (Figure 5D); this process that can be cycled hundreds of times with no measurable hysteresis. [ 55 ]…”

Biohybrid Design Gets Personal: New Materials for Patient‐Specific Therapy

“…Liu et al have looked beyond stimuli‐driven behavior that results in a permanent shape change or degradation of a cell‐laden hydrogel by developing materials that are capable of cyclic control of polymer stiffness over time . The researchers developed protein‐polymer hybrid hydrogels that could undergo reversible stiffening in response to environmental cues by engineering protein cross‐linkers that exhibit different conformations and end‐to‐end lengths in response to an external stimulus.…”

Biologically Inspired, Cell‐Selective Release of Aptamer‐Trapped Growth Factors by Traction Forces

“…[7] Recent research has enhanced our ability to imbue scaffolds with temporal information that is transiently activated by stimuli such as light, enzymes, pH, complementary ligands, or an integrated combination of multiple stimuli. [2,3,8–15]…”