MSE Colloquium: Darrin Pochan, Biomolecules for Non-biological things: Materials Construction through Peptide Design and Solution Assembly
Self-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. Furthermore, different self-assembly pathways can be utilized to reproducibly form different nanostructures with the same molecule design. Two classes of materials will be discussed. First, 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. Importantly, the hydrogels do not form until individual peptide molecules intramolecularly fold into a beta-hairpin conformation. Subsequently, specific, intermolecular assembly occurs into a branched nanofibrillar network. 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. During assembly and gelation, desired components can be encapsulated within the hydrogel network such as drug compounds and/or living cells. The system can shear thin but immediately reheal to preshear stiffness on the cessation of the shear stress. Second, a new solution assembled system comprised of coiled coil motifs designed theoretically to assemble into two-dimensional nanostructures not observed in nature will be introduced. The molecules and nanostructures are not natural sequences and provide opportunity for arbitrary nanostructure creation with peptides. New results revealing the versatility of computational design of peptide building blocks for physical and covalent interaction to build new forms of one-dimensional chains and two-dimensional network materials will be discussed.
Darrin Pochan is currently professor and chair of the Materials Science and Engineering Department as well as a member of the Delaware Biotechnology Institute at the University of Delaware. Since joining the MSE department in 1999 after a Ph.D. in Polymer Science and Engineering at the University of Massachusetts-Amherst and a National Research Council Post-doctoral fellowship at the National Institute of Standards and Technology in Gaithersburg, MD he has developed a research program around the construction of new materials and nanostructures via molecular self-assembly mechanisms, biomaterials, and materials for nanotechnology and energy applications through organic/inorganic hybrids. Honors for Darrin include an NSF Career Award, the DuPont Young Faculty Award, the Dillon medal from the American Physical Society, Fellow of the American Physical Society, Fellow of the Royal Society of Chemistry and Fellow of the Polymer Materials Science and Engineering Division of the American Chemical Society. Currently, Darrin also serves as Editor in Chief of Soft Matter, the interdisciplinary journal from the Royal Society of Chemistry in the United Kingdom.