(217m) Oxidatively-Responsive Chain Extension to Topologically Entangle Artificially Engineered Protein Hydrogels

The mechanical properties of hydrogels, including stiffness, toughness, extensibility and stability, play an important role in their biomedical applications.  Here we demonstrate topological entanglement as an effective approach to increase the mechanical tunability of a transient hydrogel network based on coiled-coil association.  Upon preparing the hydrogel in a physically entangled state, the toughness and extensibility significantly increase, while the stiffness is not greatly affected.  Entanglement suppresses the erosion of hydrogel by a factor of 5.8 and increases the stress-resistance by a factor of 12.5, which provides enhanced mechanical stability in a physiological relevant environment.  The reversible nature of disulfide bonds for chain-extending protein molecules allows to switching on and off the aforementioned mechanical enhancement by redox stimulus, which offers an opportunity to constructing mechanically-enhanced and redox responsively injectable hydrogels.  The sticky reptation theory is used to understand the entanglement effect in the hydrogel.  A constitutive modeling proves that the entanglement results in drastic reduction in network stress relaxation and leads to strain stiffening.