title: Facile fabrication of robust silk nanofibril films via direct dissolution of silk in CaCl2-formic acid solution.
abstract: In this study, we report for the first time a novel silk fibroin (SF) nanofibrous films with robust mechanical properties that was fabricated by directly dissolving silk in CaCl2-formic acid solution. CaCl2-FA dissolved silk rapidly at room temperature, and more importantly, it disintegrated silk into nanofibrils instead of separate molecules. The morphology of nanofibrils crucially depended on CaCl2 concentrations, which resulted in different aggregation nanostructure in SF films. The SF film after drawing had maximum elastic modulus, ultimate tensile strength, and strain at break reaching 4 GPa, 106 MPa, and 29%, respectively, in dry state and 206 MPa, 28 MPa, and 188%, respectively, in wet state. Moreover, multiple yielding phenomena and substantially strain-hardening behavior was also observed in the stretched films, indicating the important role played by preparation method in regulating the mechanical properties of SF films. These exceptional and unique mechanical properties were suggested to be caused by preserving silk nanofibril during dissolution and stretching to align these nanofibrils. Furthermore, the SF films exhibit excellent biocompatibility, supporting marrow stromal cells adhesion and proliferation. The film preparation was facile, and the resulting SF films manifested enhanced mechanical properties, unique nanofibrous structures, and good biocompability.
authors.affiliation: Medical College of Soochow University, Jiangsu Province Key Laboratory of Stem Cell Research, Soochow University , Suzhou 215123, China.
authors.forename: Feng
authors.initials: F
authors.lastname: Zhang
authors.forename: Xinran
authors.initials: X
authors.lastname: You
authors.forename: Hao
authors.initials: H
authors.lastname: Dou
authors.forename: Zhi
authors.initials: Z
authors.lastname: Liu
authors.forename: Baoqi
authors.initials: B
authors.lastname: Zuo
authors.forename: Xueguang
authors.initials: X
authors.lastname: Zhang
mesh_terms: D065966:Absorption, Physicochemical; D000818:Animals; D001672:Biocompatible Materials / Q000138:chemical synthesis*; D002122:Calcium Chloride / Q000737:chemistry*; D049109:Cell Proliferation / Q000502:physiology; D002470:Cell Survival / Q000502:physiology; D002478:Cells, Cultured; D003460:Crystallization / Q000379:methods; D055119:Elastic Modulus; D008297:Male; D008422:Materials Testing; D008567:Membranes, Artificial; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000502:physiology*; D057139:Nanofibers / Q000737:chemistry* / Q000648:ultrastructure; D010316:Particle Size; D017207:Rats, Sprague-Dawley; D033081:Shear Strength; D047011:Silk / Q000737:chemistry* / Q000648:ultrastructure; D012996:Solutions; D013718:Tensile Strength; D014783:Viscosity; D017155:Wettability
chemical_list: D001672:Biocompatible Materials; D008567:Membranes, Artificial; D047011:Silk; D012996:Solutions; D002122:Calcium Chloride
keywords: biocompatibility; film; mechanical property; nanofibril; silk fibroin