In this work, silk fibroin (SF) filament with fibrils regenerated by dissolving in CaCl₂-formic acid (FA) was prepared by wet-spun method at room temperature. Different from traditional dissolved methods, SF solutions obtained by dissolving in CaCl₂-FA preserved fibrils, which have been recognized as the key to the high performance of native silk. The morphology of SF filament was analyzed, very dense filaments with smooth surface and circular, nanofibrils could be observed in longitudinal and cross-sections of filaments. Moreover, the breaking stress of samples was gradually increased with the increase of draw-down ratios. After 3 times drawing, the breaking stress and elongation at break of filament were 276.4±22.6 MPa and 40.8±3.1%, respectively. At the same time, the secondary structure of SF filament was typical β-sheet. In addition, SF filaments showed excellent degradation property, the mass lost of SF filament declined 42% after incubating in protease XIV solution. Above all, the human mesenchymal stem cells (hMSCs) adhered very well on the surface of the filaments, which demonstrated the good biocompatibility of SF filaments, was suitable for application in tissue engineering.

Keywords: silk fibroin fibers, CaCl2-formic acid, fibril, morphology, biomaterials