(350c) Hierarchical Biomaterials Based On the Self-Assembly of the Silk Protein Sericin

Silk consists primarily of two proteins - a fibrous core protein, fibroin (~70%) and a glue protein, sericin (~25-30%), which envelops the fibroin fibers with sticky layers thus helping in the formation of cocoon, achieved by cementing the silk fibers together. Sericin, a water soluble protein has traditionally been discarded in silk processing, despite great potential for use as a biomaterial. Here we present results showing that this glue protein, sericin has the ability to form self-assembled nano and micro-structures with hierarchical self-similarity across length scales in the form of a diffusion-limited assembly. High-resolution atomic force microscopy was used to image and take nanomechanical measurements of the self-assembled protein. The self assembly of the sericin protein was analyzed based on the theory of diffusion limited aggregation to explain the fractal nature of these architectures observed. Using nanoindentation, the stiffness of these nanostructures was measured. The unique physical behavior, mechanical properties and fractal nature of this glue protein may represent a key step in understanding its biological relevance of sericin as well for directing the design and formation of silk-based biomaterials.