Role of Ca2+ on structures and properties of regenerated silk fibroin aqueous solutions and fibres

It has been known that the concentration of Ca2+ gradually increased along the silk gland of silkworm and it played an important role in the spinning process of silk fibre in vivo. In this work, Raman spectrometer, synchrotron radiation wide angle X-ray diffraction facility and material testing instrument were used to investigate the effect of Ca2+ on the structures and properties of regenerated silk fibroin (RSF) in its aqueous solutions and dry spun fibres. It was found that as the concentration of Ca2+ increased in the RSF aqueous solutions and fibres, the conformational transition to beta-sheet was promoted, and the resultant post-treated RSF fibre showed higher crystallinity, higher crystalline orientation as well as better mechanical properties. Therefore, it could be concluded that the addition of Ca2+ had improved the structures of RSF aqueous solutions and the resultant fibres, and it might be a feasible approach to obtaining high performance RSF fibres.