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SQI: Simpson Querry Institute

Gianneschi Lab unravels black widow’s silk secrets

Materials scientists have long been fascinated by black widow spiders, which are known to produce an array of silks with exceptional properties. The steel-like strength of their webs is rooted in their unique structures, and the specific combination of amino acids that comprise the silk fibers. Until recently, however, the process by which the spiders transform proteins into those fibers was poorly understood, and attempts to replicate the silk using synthetics were unsuccessful. “The knowledge gap was literally in the middle,” SQI faculty member Nathan C. Gianneschi said. “What we didn’t understand completely is what goes on at the nanoscale in the silk glands or the spinning duct — the storage, transformation and transportation process involved in proteins becoming fibers.”

Thanks to a research partnership with San Diego State University and funding from the Department of Defense, the mystery surrounding these processes is finally becoming clear. In collaboration with Professors Lucas Parent (Northwestern University), David Onofrei (SDSU), and Greg Holland (SDSU), Gianneschi authored a paper titled "Hierarchical Spidroin Micellar Nanoparticles as the Fundamental Precursors of Spider Silks,” which was published Oct. 22 in the Proceedings of the National Academy of Sciences. The paper challenged existing theories which posited that spider silk proteins await the spinning process as nano-size amphiphilic spherical micelles (clusters of water soluble and non-soluble molecules) before being funneled through the spider’s spinning apparatus to form silk fibers. Instead, Gianneschi et al. announced a “modified micelles theory”, which concludes that spider silk proteins do not start out as simple spherical micelles, but instead as complex, compound micelles. “We now know that black widow spider silks are spun from hierarchical nano-assemblies (200 to 500 nanometers in diameter) of proteins stored in the spider’s abdomen, rather than from a random solution of individual proteins or from simple spherical particles,” said Holland.

With this breakthrough, scientists have a new path to creating lightweight, super-strong synthetic materials, and the potential practical applications are nearly limitless. In an interview with Northwestern Now, Gianneschi said, “One cannot overstate the potential impact on materials and engineering if we can synthetically replicate this natural process to produce artificial fibers at scale.” View published study.