Collaborative Research: Controlling Microstructure in Resilin-based Hydrogels: Linking Microscale Mechanical Properties to Behavior

University Of Massachusetts Amherst, Amherst MA

Investigators

Abstract

ABSTRACT Non-technical: Elastomeric proteins in living organisms provide outstanding mechanical properties to tissues such as skin and muscle, and generally exist in heterogeneous structures that provide mechanical reinforcement. Materials engineering approaches that enable the production of elastomeric materials with defined structures would thus have enormous potential in applications ranging from protective materials, drug delivery, and regenerative medicine. PIs approaches for producing such materials employ resilin, an insect protein that has among the best elastomeric properties reported; resilins are able to deform to a large extent and completely recover their original shape. PIs will use resilin-like proteins that are designed with specific mechanical and biological function and make materials that comprise these proteins and commonly employed synthetic polymers. Simple processing protocols with light-initiated chemistries will be used to generate hybrid materials of different compositions and predictable structures. Novel characterization methods will be used to characterize the mechanical properties of individual domains and determine structure-function relationships in this class of soft materials. The research in this program has the potential to not only impact societal needs in energy and medicine, but also educational activities for students of a variety of ages and experience. A series of workshops and student-initiated activities, in which the PIs will participate, will help transfer concepts of this program into biomaterials technologies. Technical: Of many approaches to generate 3D heterogeneity in hydrogels, the use of polymer-based microparticle composites has been of significant interest, given the many opportunities to engineer particle size, surface area, and chemistry. The development of simple, one-step methods to generate microstructured protein-polymer matrices would thus offer significant advantages for making heterogeneous materials for systematic study. We propose to exploit the well behaved phase separation of solutions of the highly elastomeric polypeptide resilin (RLP), to form microstructured hydrogels. The RLPs exhibit outstanding elastomeric and physicochemical properties that will advance the utility of the resulting materials, particularly in the development of models to understand energy dissipation in soft hydrogels. The PIs will functionalize RLPs so that they are competent for photo-initiated crosslinking, and will map the phase separation of RLP and solutions of synthetic polymers. This fundamental information will allow PIs to identify appropriate compositions and processing conditions for photocrosslinking the solutions into microstructured hydrogels that have domains of defined compositions and mechanical properties. Two distinct chemical modifications of the RLPs will allow PIs to probe the local mechanical properties of the domains and the impact of the domains on hydrogel deformation. The microstructure of the hydrogels will be characterized via microscopy methods, while the mechanical properties will be characterized via a suite of atomic force microscopy, cavitation rheology, small-strain contact mechanics, blunt puncture mechanics, and bulk oscillatory rheology. Given the wealth of target applications and the widespread use of hydrogel materials, proposed studies will in the long term advance the use of microstructured elastomeric hydrogels in applications such as energy storage, protective gear, drug delivery, and regenerative medicine. PIs will facilitate the transfer of these concepts into technological applications by hosting a series of workshops and activities for students from the secondary to postgraduate levels.