Abstract

Material Control Through Peptide Design and Solution Assembly: Injectable Solid Hydrogels

Darrin Pochan, Professor, University of Delaware

Solution assembly of molecules is an attractive materials construction strategy due to its simplicity in application.  By considering peptidic molecules in the bottom-up materials self-assembly design process, one can take advantage of inherently biomolecular attributes; intramolecular folding events, secondary structure, and electrostatic interactions; in addition to more traditional self-assembling molecular attributes such as amphiphilicty, to define hierarchical material structure and consequent properties.  These self-assembled materials range from hydrogels for biomaterials to nanostructures with defined morphology and chemistry display for inorganic materials templating.  Hydrogels, hybrid materials and nanostructure manipulation will be discussed.  The local nano- and overall network structure, and resultant viscoelastic and cell-level biological properties, of hydrogels that are formed via beta-hairpin self-assembly will be presented.  These peptide hydrogels are potentially excellent scaffolds for tissue repair and regeneration due to inherent cytocompatibility, porous morphology, and shear-thinning but instant recovery viscoelastic properties. Slight design variations of the peptide sequence allow for tunability of the self-assembly/hydrogelation kinetics as well as the tunability of the local nanostructure and hierarchical network structure. During assembly and gelation, desired components can be encapsulated within the hydrogel network such as drug compounds and/or living cells.  Importantly, once formed into a solid, self-supporting gel the network can be disrupted by the introduction of a shear stress.  The system can shear thin but immediately reheal to preshear stiffness on the cessation of the shear stress.  This shear thinning behavior of these physical networks makes them interesting candidates for injectable delivery in vivo where no post injection chemistry is required to set up the network.  Studies revealing an advantageous drug release profile after weeks in vitro will be discussed.  Furthermore, new, designed peptides that alter the fibril nanostructure and hydrogel properties will be discussed to show how molecular changes can be manifested in bulk property changes.