Developing Aciniform Spider Silk Biomaterials with Unique Structural Transitions and Properties
Abstract
Although a great deal is known about spider dragline silk, little information is available regarding the other types of spider silk, specifically aciniform silks, which are reportedly 50% tougher than dragline fibers. Therefore, the overall goal of this project is to fundamentally understand the molecular protein structure and its mechanical and physical properties to discern higher-order assembly of these exceptional silks, and further understand the biochemical processing conditions for silk fiber formation. Our innovative hypothesis with regards to aciniform silk is that it has unique mechanical, physical and structural features that make it an ideal material for a diverse range of bioinspired ARO applications. The novel features of aciniform spider silk include: (1) its smaller fiber diameter, 500 nm, an order of magnitude finer than the commonly studied dragline spider silks, (2) extremely high toughness surpassing all man-made materials due to its hybrid helical coiled-coil/b-sheet molecular architecture and (3) its unique hydration-induced cross-linking feature that has been discovered in our lab. Aciniform silks exhibit a novel interaction with water that has not been observed in other spider or animal silks that make it ideal for inspiring a new class of biomaterials. Aciniform silk fibers convert from a primarily flexible helical structure to a stiff, cross-linked b-sheet mat when water-treated (hydration/dehydration). One can envision using this distinct hydration-induced cross-linking molecular switch in applications that would benefit from an ability to transform from a highly flexible fiber to a rigid cross-linked b-sheet matrix merely by wetting with water. It is anticipated that such a material could be used for a number of ARO applications including advanced textiles for protective clothing, tents, parachutes and repairs of such materials. In the proposed work we will characterize both the native silk protein as stored within the silk gland, and also investigate the physical and structural properties of freshly-spun aciniform silk fibers in both their natural (dry) and water-wetted states. Physical characterization methods will include mechanical testing, solution and solid-state NMR spectroscopy, X-ray diffraction and cryo-TEM. The hypothesis is that understanding the molecular structure, dynamics and assembly process of native aciniform spider silk will provide a fundamental basis for developing a new class of biomaterials that have physical and mechanical properties that mimic aciniform spider silk. To address this hypothesis, we will first build upon our recent comprehensive solid-state NMR data on native aciniform fibers as a basis for the plans. We will examine the molecular structure and dynamics of native aciniform silk with a focus on NMR, X-ray Diffraction and cryo-TEM techniques. We expect to gain improved insight into how aciniform spider silk assembles at a molecular level by investigating the gland fluid to better design and optimize biomaterial processing. The expectation with this new insight would be profound; from new modes to produce these types of materials and new ideas on how to exploit helical coiled-coil hybrid b-sheet aciniform biomaterials that display unique structural transitions and properties that resemble the native material.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 09, 2020
- Source ID
- W911NF2010143
Entities
People
- Gregory Holland
Organizations
- Army Contracting Command
- Salk Institute for Biological Studies
- United States Army