(521c) Polypeptide Templating of Structural Proteins for Tailored Hierarchical Materials

Materials generation in nature often involves the use of templates to regulate phase transformation and subsequent hierarchical organization of nanoscale building blocks, with the most prominent examples being biomineralization and amyloid fibrils growth, to name a few. Despite recent progress in directing the assembly of biomacromolecules into well-defined nanostructures, leveraging pathway complexity of molecular disorder to order transition while bridging materials fabrication from nano- to macroscale remains an open challenge. In this presentation, we introduce templated crystallization of structural proteins as a process to nanofabricate hierarchically structured materials up to centimeter scale, using silk fibroin as an example. The process involves the use of ordered peptide supramolecular assemblies as templates to drive a phase transformation of silk fibroin from unordered to ordered conformations, thereby enabling further assembly of the silk fibroin chains into nanostructured materials (i.e. β-sheeted nanofibrils). Multiple parameters including the relative concentration between silk fibroin and peptide seeds, silk fibroin molecular weight, pH and peptide conformation are investigated to fine tune the assembly kinetics and silk polymorphs. Templated crystallization coupled with various top-down fabrication such as soft lithography and printing enables (i) epitaxial materials growth from the molecular level (i.e. disordered silk fibroin molecules) all the way up to centimeter scale in an exquisite single-pot, bottom-up system; (ii) surface functionalization with topographical control over nanofibrils assembly on pre-deposited peptide seeds; and (iii) three-dimensional manipulation of silk nanofibrils into macroscopic structures with customized shapes and controlled anisotropy. Together, these results pave the way for nanofabrication of a new generation of smart and adaptive materials built from the bottom up.