Gelation behavior of regenerated silk fibroin solution

초록

The mechanisms of silk processing and fiber formation are not completely understood because of the complicated transport phenomenon and gel-sol transitions. To elucidate mechanisms of silk processing and fiber formation, it is necessary to investigate the aggregation of silk fibroin in solution and gel states. In this study, we prepared regenerated silk fibroin (SF) solution at various concentrations and examined the influence of temperature, pH and concentration of ions such as calcium, potassium on the gelation of aqueous SF solution. Morphological and structural features of these solutions were examined in order to correlate solution conditions with transitions. Gelation time of aqueous SF solution decreased with increase in silk fibroin content and temperature. Gels prepared from 4% SF solution contained large interconnected pores at 37 Celsius degree and 60 Celsius degree. Gels prepared from 8-12% SF solution showed a network and sponge-like structures. As the concentration of silk fibroin increased, these structures disappeared and were transformed into aggregate structures. From X-ray diffraction patterns, these gels showed silk II structure on the basis of the rings at 9.7 and 4.3 Angstron. Calcium ions resulted in shorter gelation time than potassium ions at the same concentrations at 37 Celsius degree and 60 Celsius degree. Higher calcium ion concentrations resulted in longer gelation time, whereas there was no difference in potassium ions. Gels prepared from SF solution containing calcium and potassium ions showed small interconnected pores. With increase in ion concentrations, gel showed dense and aggregate structures. With more complete mapping of the influence of solution variables on structure and morphological transitions, we anticipate new options for the biomimetic processing of silk fibroin into new materials.