Raman, WAXS, and Solid-State NMR Characterizations of Regenerated Silk Fibroin Using Lanthanide Ions as Chaotropic Agents

Bombyx mori silk fibroin(SF) hasbeen reported as a convenient natural material for regenerative medicine,optoelectronics, and many other technological applications. SF owesits unique features to the hierarchical organization of the fibers.Many efforts have been made to set up protocols for dissolution sincemany applications of SF are based on regenerated solutions and fibers,but chaotropic conditions required to disassemble the packing of thepolymer afford solutions with poor crystalline behavior. Our previousresearch has disclosed a dissolution and regeneration process of highlycrystalline fibers involving lanthanide ions as chaotropic agents,demonstrating that each lanthanide has its own unique interactionwith SF. Herein, we report elucidation of the structure of Ln-SFfibers by the combined use of Raman spectroscopy, wide-angle X-rayscattering (WAXS), and solid-state NMR techniques. Raman spectra confirmedthe coordination of metal ions to SF, WAXS results highlighted thecrystalline content of fibers, and solid-state NMR enabled the assessmentof different ratios of secondary structures in the protein.

Automated summary

Bombyx mori silk fibroin (SF) is a natural material with various applications in regenerative medicine, optoelectronics, and other fields. The unique features of SF are attributed to the hierarchical organization of its fibers. Previous research has discovered a dissolution and regeneration process using lanthanide ions as chaotropic agents, and this study further elucidates the structure of Ln-SF fibers using Raman spectroscopy, wide-angle X-ray scattering (WAXS), and solid-state NMR techniques.