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Silk dissolution and regeneration at the nanofibril scale.

Native silk features strong, extensible and tough properties which originate from its hierarchical nanofibril structure. In the present study, native silk nanofibrils were obtained by dissolving degummed silk in salt-formic acid (FA), such as CaCl2-FA. The CaCl2-FA dissolved silk by breaking hydrogen bonds in the crystalline region while preserving the nanofibril structures. The dissolution behavior of silk from fibre to nanofibril was determined by Na2CO3 concentration during the degumming process, and was regulated by CaCl2 concentration during the dissolution process. The resulting solution containing silk fibroin (SF) nanofibrils could be easily processed into films with nanofibrous structures and high strength. In addition, high-quality electrospun SF nanofibres could also be generated easily from this solution. The novel dissolution and regeneration behavior of silk at the nanofibril scale provides new insights into methods for the preparation of high-quality silk materials for application in high-tech areas.