(86b) Responsive Gel-Gel Transitions in Artificially Engineered Protein Hydrogels

Artificially engineered protein hydrogels provide an attractive platform for biomedical materials due to their similarity to components of the native extracellular matrix.  Engineering responsive transitions between shear-thinning and tough gel phases in these materials could potentially enable gels that are both shear-thinning and tough to be produced as novel injectable biomaterials.    To engineer a gel with such transitions, a triblock copolymer with thermoresponsive polymer endblocks and an artificially engineered protein gel midblock is designed.  Temperature is used to trigger a transition from a single network protein hydrogel phase to a double network phase with both protein and block copolymer networks present at different length scales.  The formation of the second network is shown to produce a large, nonlinear increase in the elastic modulus as well as enhancements in creep compliance and toughness.  A second approach to biomaterial toughening is explored through engineering both topological entanglements and physical associations into the gel to produce two distinct length and timescales of network interaction.  Using oxidatively responsive chemistry enables entanglements to be produced dynamically within the material, enabling responsive enhancement of the work required for plastic deformation.