Cytoskeleton-Inspired Artificial Protein Design to Enhance Polymer Network Elasticity

Abstract

Reducing topological network defects to enhance elasticity in polymeric materials remains a grand challenge. Efforts to control network topology, primarily focused on crosslinking junctions, continue to underperform compared to theoretical estimations from idealized networks using affine and phantom network theories. Here, artificial protein technology was adapted for the design of polymer-network hydrogels with precisely defined coil-like and rod-like strands to observe the impact of strand rigidity on the mechanical properties of polymeric materials. Cytoskeleton-inspired polymer-network hydrogels incorporated with rod-like protein strands nearly tripled the gel shear elastic modulus and relaxation time compared to coil-like protein strands, indicating an enhanced effective crosslinking density. Furthermore, asymmetric rod-coil protein designs in network strands with an optimal rod:coil ratio improved the hydrogel relaxation time, enhancing the stability of physical macromolecular associations by modulating crosslinker mobility. The careful design of strand rigidity presents a new direction to reduce topological defects for optimizing polymeric materials.

Non-Covalently Associated Streptavidin Multi-Arm Nanohubs Exhibit Mechanical and Thermal Stability in Protein-Network Materials

“…This measurement is within the 500 Pa range from prior studies that developed hydrogels using other SpyTag-SpyCatcher design strategies. 15,47 However, this G′ is weak relative to other protein-network materials with similar molecular weight and is significantly lower than the predicted G′ based on the polymer-network models 20,38 (Table S2). The experimental G′ is approximately 1% of the theoretical G′ from the affine and phantom polymer network models.…”

“…Artificial Protein with Tetra-SAv Cross-linkers. To analyze the properties of proteinnetwork materials composed of tetra-SAv cross-linkers, we designed an artificial protein containing a SAv monomer on each end connected by an intrinsically disordered, flexible, polyelectrolyte-like protein containing 24 repeats of AGAGAGPEG amino acid sequence, denoted as C24, 27,38 which resulted in SAv-C24-SAv proteins (Table S1). We expected that SAv monomers in SAv-C24-SAv proteins would self-recognize and self-associate to form SAv homotetramers in aqueous buffer and develop hydrogels, similar to other well-known, noncovalently associating protein hydrogels.…”

“…The experimental G′ was expected to be lower than the theoretical G′ since it is well-known that there are topological defects, such as self-loops and dangling chains, in polymer/protein networks with flexible strands. 20,37,38 However, we see a significant improvement in hydrogel fabrication and G′ when replacing the SpyTag-SpyCatcher mechanism (𝑓 = 2) to a more controllable dityrosine photo-crosslinking (𝑓 = 2). This confirms that controlling the secondary crosslinking allows enough time for these crosslinkers to diffuse throughout the protein network before permanent chemical bond formation, which is crucial in improving mechanical properties or effective junctions in the network.…”

Protein Hydrogels: The Swiss Army Knife for Enhanced Mechanical and Bioactive Properties of Biomaterials

“…Another class of responsive protein hydrogels involves self-assembly in response to a complementary protein or particle to create composites. This physical recognition enables modulation of mechanical and structural properties during the assembly process as well as specific self-healing after stress application [ 134 , 135 , 136 , 137 ]. For example, modular proteins containing an elastomeric domain and a leucine zipper domain are able to self-associate into hydrogels and thermo-reversibly transit back to solution form at temperatures over 60 °C [ 138 ].…”

Monomer‐scale design of functional protein polymers using consensus repeat sequences

“…To investigate the impact of chain stiffness in polymer network elasticity, consensus ankyrin repeat domains were genetically fused between associative domains to produce tri-block protein polymers. 228 The resulting proteins formed hydrogels with nearly three times higher elastic moduli when compared to hydrogels comprising tri-block proteins with random coil midblock domains. An exploration of rod-like, coil-like, and rod-coil architectures demonstrated the promise of ankyrin repeat domains to modulate the mechanical properties of an emerging class of protein hydrogels.…”