(673j) Elucidation of Self-Assembly of Silk Fibroin Proteins into Functional Biomaterials

After billions of years of evolution, nature has learned what works, what is appropriate, and what lasts. We aim to understand related phenomena and associated principles responsible for nature's building blocks and then to selectively adapt ideas from nature in order to engineer novel materials with unique and superior properties. In our research laboratory, mussels, silk, and lotus leaves are three key natural systems from which we get inspiration, particularly regarding their chemistry, composition, and structure. In this presentation, the structure-property relationships of Bombyx mori silk fibroin (SF) proteins will be discussed. Materials fabricated from SF proteins have been known to exhibit excellent eco/biocompatibility, biodegradability, and tunable mechanical properties. Although many applications of silk rely on thin films and sub-micron feature sizes, mechanisms and dynamics on the formation of specific structures (e.g. microneedles, spun fibers, or thin films) at the microscopic level have not been well addressed. In particular, there is a limited amount of information on how such structures self-assemble from their constituent molecules (i.e. SF proteins) and how the SF proteins interact with each other and behave in solution under nanoconfined environments. This presentation summarizes our recent studies and findings in this context. We have studied how SF protein polymers aggregate or bundle to form continuous fibers when they are pressed together and/or sheared against each other, using the Surface Forces Apparatus (SFA), as well as various mechanical characterization and microscopy imaging techniques. The presentation also involves the discussion and comparison of the complex dynamics of force profiles for SF proteins with other protein-based phenomena. We anticipate that the study of dynamics and self-assembly SF protein polymers is not only of fundamental research value, but also of practical significance for better designing and fabricating novel and reliable SF-based materials in nanoscale.