(725d) Bio-Inspired, Hierarchically Structured Hydrogels Comprised of Polypeptide Micelles: A Platform for Tunable, Mechanically Robust, and Functional Soft Materials

Authors: 
Ghoorchian, A., Duke University
Simon, J., Duke University
Lopez, G. P., Duke University
Chilkoti, A., Duke University

Many non-covalently crosslinked hydrogels exhibit poor mechanical properties, which significantly limit their utility in load-bearing applications. To address this limitation, we designed and constructed hydrogels comprised of micelles created from genetically engineered, amphiphilic, elastin-like polypeptides (ELPs). We form these temperature responsive monodisperse micelles by heating them above their lower critical solution temperature (LCST) and then crosslinking them through metal coordination. The metal binding peptide is displayed on micelles’ coronae and we designed it based on a naturally occurring metal coordination the sequence found in matrix metalloproteinase. These hydrogels exhibit hierarchical structure, are stable over a large temperature range, and exhibit tunable stiffness, self-healing and fatigue resistance. Gels with polypeptide concentration of 10% w/v and higher show storage moduli of ≈1 MPa from frequency sweep tests and exhibit self-healing within minutes. These reversibly crosslinked, hierarchical hydrogels with enhanced mechanical properties have potential utility in a variety of biomedical applications.

As a potential application for micellar gels, we developed a micelle-shedding hydrogel that releases micelles containing small hydrophobic molecules in their cores. We have shown that the release can be tuned over several days in physiological conditions. For this system, we crosslinked the micelles through metal binding domains and then to control their release, we entrapped them in a covalently crosslinked polypeptide network. Micelle shedding rate is a function of the chemical potential difference between the gel and the surrounding environment. We showed that crosslinking density, micelle concentration, and chemical potential could all be used to adjust the release rate of the micelles from the gels.