Preparation of Natural Spider Silk Nanofibrils by Assembling Molecules or Disassembling Fibers

Spider silk features a remarkable combination of strength and toughness, which outperform many of the known materials. Additionally, its biocompatibility, biodegradability, and lightweight create numerous potential applications. Despite extensive research, comprehensive experimental evidence of the formation and morphology of the internal structure of this biopolymer is still limited and controversially discussed. Here, we disassembled spider silk fibers by mechanical force and showed that it is completely composed of ≈10 nm nanofibrils aligned in the fiber direction. The extreme stability and the robustness of these nanofibrils reveal that they give birth to fiber's outstanding mechanical performance. Furthermore, we observed that the silk protein possesses an intrinsic mechanism to form nanofibrils of the same dimensions and morphology as the disassembled natural nanofibrils via shear-induced self-assembly, which can be easily triggered in-vitro. Finally, we studied the self-assembly under varying physicochemical conditions and found it is highly sensitive to pH, shear force, ion concentration, and protein concentration. This knowledge helps to understand the fundamentals of this exceptional material, paving the way for the realization of silk-based high-performance materials.