Developing Spider-Silk-Model Artificial Fibers by A Chemical Synthetic Approach 

Description

Spider-dragline-silks (SDS) have extraordinarily high strength, high modulus, large extensibility, thus high toughness simultaneously, which makes them the most desirable materials in the world for high performance applications such as space-suits, bulletproof- vests, balloon parachutes, medical devices and specialty ropes. Up to now, however, mass production of artificial SDS is still a dream even though tremendous worldwide efforts have been made, especially in genetic engineering of spider-silk proteins (spidroins). From scalability and cost viewpoint, ideal methods for making artificial spider-silk-model (SSM) polymers, namely, artificial spidroins, should follow chemical synthetic route. The problems of existing chemical syntheses in limited and scattered researches are: (1) synthesis process is inefficient; (2) molecular weight of the artificial spidroins is low; (3) mechanical properties of the resultant fibers/polymers are extremely unsatisfactory. Based on our recent achievements in peptide-polyurethane/ Urea, namely, a very stretchable animo-acid-containing polymer with 10 times strength of normal polyurethane, and inspired by spider-silk hierarchical structure, here we propose a simple and efficient chemical synthetic approach to construct all-amino- acids (AAA), high-molecular-weight spider-silk-model (SSM) polymers for forming SDS performance fibers through a bionic matching spinning process. For the above purpose, we will first fabricate essential spider-silk structural building blocks: β-sheet and α-helix forming polypeptides respectively using ring-opening-polymerization (ROP) of amino-acids, which are then connected by lysine isocyanate to form a small urea-linkage (bridge-link) between them. This results in an AAA polymers/copolypeptide as artificial-spidroin. The bridge-link has similarity to the peptide-bond in protein backbone and is well-established in synthesis, enabling high-molecular- weight and scalable production. Molecular self-assembly of artificial-spidroins will then be studied with advanced techniques such as Fourier Transfer Infrared, Transmission and Scanning Microscopes and Atomic Resolution Tomography in terms of their primary to quaternary structures. A bionic dry spinning will ensure fibril hierarchical structures during fiber forming. The effects of different factors on fiber mechanical performance of strength, modulus and extensibility will be systematically examined including chemical composition, spinning conditions, β- crystals, α-helix and amorphous regions. The hierarchical structure of the resultant SSM fibers will be investigated and theoretical models for optimal performance will be established. The work being proposed in this project will directly provide an effective fabrication method of SSM materials and provide a research model for understanding the composition-structure-property relationship of protein materials with hierarchical structures. More importantly, this work will lay a solid foundation for speeding up the commercialization process, which can realize the dream for spider-silk like materials.