Sustainable Spinning of Artificial Spider Silk Fibers with Excellent Toughness and Inherent Potential for Functionalization

Despite impressive progress in the field, there are still several major bottlenecks in producing fibers from recombinantly produced spider‐silk‐like proteins to replicate the extraordinary mechanical properties of spider major ampullate silk. The conventional artificial fiber spinning processes rely primarily on organic solvents to coagulate proteins into fibers and require complex post‐treatments to obtain fibers with valuable properties. This is due to challenges in obtaining soluble silk proteins, but also because the native silk spinning process leading to the hierarchical organization of the silk proteins is not fully understood and is hard to replicate in a manner applicable to industrial settings. Here, recombinant spider‐silk fusion proteins are efficiently produced and processed into as‐spun fibers with a toughness modulus of 120 MJ m−3 and extensibility of 255% using solely aqueous solutions. The spider‐silk fusion proteins assemble in a manner similar to that reported for native spider silk: they phase separate induced by salting out, followed by alignment and a secondary structure transition triggered by shear forces and dehydration. Finally, the design of the fusion silk proteins enables straightforward functionalization of the fibers under mild all‐aqueous conditions via a simple biomolecular click reaction both pre‐ and post‐spinning.