Orientational behaviors of silk fibroin hydrogels

In this study, a novel shear-induced silk fibroin (SF) hydrogel with three-dimensional (3D) anisotropic and oriented gel skeleton/network morphology is presented. Amphipathic anionic and nontoxic sodium surfactin is blended with the SF to decrease its gelation time during the mechanical shearing process. The fibroin/surfactin blended solutions undergo a facial shearing process to accomplish a sol-gel transition within 1 hour. The dynamic sol-gel transition kinetic analysis, gel skeleton/network morphology, and mechanical property measurements are determined in order to visualize the fibroin/surfactin sol-gel transition during the shearing process and its resulting hydrogel. The results demonstrate that there is significant beta-sheet assembly from random coil conformations in the fibroin/surfactin blended system during the facile shearing process. The SF beta-sheets further transform into a fibrous large-scale aggregation with orientational and parallel arrangements to the shearing direction. The shear-induced fibroin/surfactin hydrogel exhibits notable anisotropic and oriented 3D skeleton/network morphology and a significant mechanical compressive strength in proportion to the shearing stress, compared with the control fibroin/surfactin hydrogel undergoing no shearing process. Due to its oriented gel skeleton/network structure and significantly enhanced mechanical properties, the shear-induced fibroin/surfactin gel may be suitable as a biomaterial in 3D oriented tissue regeneration, including for nerves, the cultivation of bone cells, and the repair of defects in muscle and ligament tissues.(C) 2017 Wiley Periodicals, Inc.