Identification of Wet-Spinning and Post-Spin Stretching Methods Amenable to Recombinant Spider Aciniform Silk

Spider silks are outstanding biomaterials with mechanical properties that outperform synthetic materials. Of the six fibrillar spider silks, aciniform (or wrapping) silk is the toughest through a unique combination of strength and extensibility: In this study, a wet-spinning method for recombinant Argiope trifasciata aciniform spidroin (AcSpl) is introduced. Recombinant AcSp1 comprising three 200 amino acid repeat units was solubilized in a 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP)/water mixture, forming a viscous alpha-helix enriched spinning dope, and wet-spun into an ethanol/water coagulation bath allowing continuous fiber production. Post-spin stretching of the resulting wet-spun fibers in water significantly improved fiber strength, enriched beta-sheet conformation without complete alpha-helix depletion, and enhanced birefringence. These methods allow reproducible aciniform silk fiber formation, albeit with lower extensibility than native silk, requiring conditions and methods distinct from those previously reported for other silk proteins. This provides an essential starting point for tailoring wet spinning of aciniform silk to achieve desired properties.