Formation kinetics and fractal characteristics of regenerated silk fibroin alcogel developed from nanofibrillar network

The formation mechanism of RSF alcogel was elucidated from morphological observations using TEM, AFM and confocal laser scanning microscopy (CLSM) as well as the kinetic studies by Thioflavin T fluorescence and rheological methods. An intriguing dual-structure—a nanofibrillar network on the nanoscale and a floc-like network on the microscale—was observed within the RSF alcogel. Based on our kinetic study, the fractal dimension of the ramified fibrillar aggregate was found to be 2.4–2.8 depending on RSF concentration. Meanwhile, through a scaling analysis of the mechanical properties of RSF alcogels, the fractal dimension of the floc-linked network was found to be 2.2. Furthermore, our results showed that fibrillarization of RSF was triggered by a dramatic change in the interaction between RSF and cosolvent, and the gelation kinetics could be tuned by adjusting the concentration of ethanol as well as RSF. The controllable dual-structure and kinetics make such biopolymer gel a potential candidate for applications in nanotechnology.