Structures of silk fibroin before and after spinning and biomedical applications

Silkworms produce silk fibroin fibers from an aqueous silk fibroin solution by applying shear stress within the spinneret at ambient temperature. This process is an attractive model for developing sustainable fiber processing technology. However, to completely elucidate the fibroin processing mechanism, the structures of fibroin before and after spinning need to be determined. In this study, we report the structures of silk fibroin before and after spinning, determined by solution and solid-state nuclear magnetic resonance (NMR). The pre-spinning structure of fibroin tandem repeat sequences was determined by solution NMR, using native liquid silk extracted from silkworm larvae. In addition, the precise lamellar structure of fibroin after spinning was investigated through a combination of stable isotope labeling of model peptides and solid-state NMR. Moreover, a silk-based small diameter vascular graft was developed by electrospinning and was subsequently evaluated in vivo. These studies may provide a perspective for investigation of energy-conserving fiber processing techniques and silk-based biomedical materials.