title: Controllable transition of silk fibroin nanostructures: an insight into in vitro silk self-assembly process.
abstract: Silk fiber is one of the strongest and toughest biological materials with hierarchical structures, where nanofibril with size <20nm is a critical factor in determining its excellent mechanical properties. Although silk nanofibrils have been found in natural and regenerated silk solutions, there is no way to actively control nanofibril formation in aqueous solution. This study shows a simple but effective method of preparing silk nanofibrils by regulating the silk self-assembly process. Through a repeated drying-dissolving process, a silk fibroin solution composed of metastable nanoparticles was first prepared and then used to reassemble nanofibrils with different sizes and secondary conformations under various temperatures and concentrations. These nanofibrils have a similar size to that of natural fibers, providing a suitable unit to further assemble the hierarchical structure in vitro. Several important issues, such as the relationships between silk nanofibrils, secondary conformations and viscosity, are also investigated, giving a new insight into the self-assembly process. In summary, besides rebuilding silk nanofibrils in aqueous solution, this study provides an important model for furthering the understanding of silk structures, properties and forming mechanisms, making it possible to regenerate silk materials with exceptional properties in the future.
authors.affiliation: National Engineering Laboratory for Modern Silk, College of Textile and Clothing Engineering, Soochow University, Suzhou 215123, People's Republic of China.
authors.forename: S
authors.initials: S
authors.lastname: Bai
authors.forename: S
authors.initials: S
authors.lastname: Liu
authors.forename: C
authors.initials: C
authors.lastname: Zhang
authors.forename: W
authors.initials: W
authors.lastname: Xu
authors.forename: Q
authors.initials: Q
authors.lastname: Lu
authors.forename: H
authors.initials: H
authors.lastname: Han
authors.forename: D L
authors.initials: DL
authors.lastname: Kaplan
authors.forename: H
authors.initials: H
authors.lastname: Zhu
mesh_terms: D001672:Biocompatible Materials / Q000138:chemical synthesis*; D003460:Crystallization / Q000379:methods*; D055119:Elastic Modulus; D005349:Fibroins / Q000737:chemistry* / Q000648:ultrastructure*; D046911:Macromolecular Substances / Q000737:chemistry; D008422:Materials Testing; D008968:Molecular Conformation; D057139:Nanofibers / Q000737:chemistry* / Q000648:ultrastructure*; D010316:Particle Size; D044367:Phase Transition; D013499:Surface Properties; D013718:Tensile Strength; D014783:Viscosity
chemical_list: D001672:Biocompatible Materials; D046911:Macromolecular Substances; C482288:fibroin, silkworm; D005349:Fibroins