Rationally Designed Dynamic Protein Hydrogels with Reversibly Tunable Mechanical Properties

Abstract

Protein hydrogels have attracted considerable interest due to their potential applications in biomedical engineering. Creating protein hydrogels with dynamic mechanical properties is challenging. Here, the engineering of a novel, rationally designed protein-hydrogel is reported that translates molecular level protein folding-unfolding conformational changes into macroscopic reversibly tunable mechanical properties based on a redox controlled protein folding-unfolding switch. This novel protein folding switch is constructed from a designed mutually exclusive protein. Via oxidation and reduction of an engineered disulfi de bond, the protein folding switch can switch its conformation between folded and unfolded states, leading to a drastic change of protein's effective chain length and mechanical compliance. This redox-responsive protein can be readily photochemically crosslinked into solid hydrogels, in which molecular level conformational changes (foldingunfolding) can result in signifi cant macroscopic changes in hydrogel's physical and mechanical properties due to the change of the effective chain length between two crosslinking points in the protein hydrogel network. It is found that when reduced, the hydrogel swells and is mechanically compliant; when oxidized, it swells to a less extent and becomes resilient and stiffer, exhibiting an up to fi vefold increase in its Young's modulus. The changes of the mechanical and physical properties of this hydrogel are fully reversible and can be cycled using redox potential. This novel protein hydrogel with dynamic mechanical and physical properties could fi nd numerous applications in material sciences and tissue engineering.

Protein Fragment Reconstitution as a Driving Force for Self‐Assembling Reversible Protein Hydrogels

“…The G N and G C fragments we used within this study each carry one cysteine residue (Cys41 and Cys43); the location of the two cysteine residues allows for the formation of a disulfi de bond in the folded GL5CC form under oxidizing conditions (Figure 1 A). [ 34,37 ] If this conversion can be accomplished in the hydrogel, the physically crosslinked hydrogel can thus be converted into a chemically crosslinked hydrogel, potentially improving the hydrogel's thermal stability signifi cantly.…”

“…2015, 25, 5593-5601 www.afm-journal.de www.MaterialsViews.com the loop of the host protein GL5). [ 33,37 ] GL5-I27 can be considered as G N -I27-G C ; since I27 is thermodynamically more stable than GL5, the thermodynamically stable conformation of GL5-I27 is GL5(U)-I27(F), in which GL5 is unfolded and I27 is folded. Thus, in this mutually exclusive protein GL5-I27 (G N -I27-G C ), intramolecular fragment reconstitution is prevented.…”

“…Thus, in this mutually exclusive protein GL5-I27 (G N -I27-G C ), intramolecular fragment reconstitution is prevented. In our previous work, we constructed chemically crosslinked protein hydrogels using the polyprotein GB1-R-(GB1-GL5CC-I27-R) 2 , [ 37 ] which can be represented as GR(G-G N -I27-G C -R) 2 . This protein can be considered tetrafunctional in terms of crosslinking, where the fragment reconstitution of G N and Gc from neighboring molecules can reconstitute the folded GL5 domain via domain swapping.…”

Photoresponsive Elastic Properties of Azobenzene-Containing Poly(ethylene-glycol)-Based Hydrogels

“…Changes in protein conformation can also be used to confer dynamic properties to a hydrogel. 6, 7 For example, Kong et al took an innovative approach to reversibly controlling modulus in protein hydrogels by using redox chemistry to fold and unfold the protein, thereby altering the crosslinker length. 6 Effects of the changes in oxidation state on cells have yet to be explored.…”

Spatially and temporally controlled hydrogels for tissue engineering

“…For example, genetically engineered protein-based hydrogels showed the potential to transfer the change in protein conformation to differences of the macroscopic properties of hydrogels [307–309]. Very recently, dynamic hydrogels that were responsible for external magnetic field were demonstrated with stiffness change of several orders of magnitude, which could be applied to modulate stem cell behavior including osteogenesis and secretion of proangiogenic molecules [310].…”