Alteration of Microstructure in Biopolymeric Hydrogels via Compositional Modification of Resilin-Like Polypeptides.

Heterogeneities in hydrogel scaffolds are known to impact the performance of cells in cell-laden materials constructs, and we have employed the phase separation of resilin-like polypeptides (RLPs) as a means to generate such materials. Here, we study the compositional features of resilin-like polypeptides (RLPs) that further enable our control of their liquid-liquid phase separation (LLPS) and how such control impacts the formation of microstructured hydrogels. The evaluation of the phase separation of RLPs in solutions of ammonium sulfate offers insights into the sequence-dependent LLPS of the RLP solutions, and atomistic simulations, along with 2D-nuclear Overhauser effect spectroscopy (NOESY) and correlated spectroscopy (COSY) 1H NMR, suggest specific amino acid interactions that may mediate this phase behavior. The acrylamide functionalization of RLPs enables their photo-cross-linking into hydrogels and also enhances the phase separation of the polypeptides. A heating-cooling protocol promotes the formation of stable emulsions that yield different microstructured morphologies with tunable rheological properties. These findings offer approaches for choosing RLP compositions with phase behaviors that can be easily tuned with differences in temperature to control the resulting morphology and mechanical behavior of the heterogeneous hydrogels in regimes useful for biological applications.