Conformation transition of silk fibroin induced by blending degummed silk

Fibroin has attracted considerable interest in biomedical and biotechnological applications because of the outstanding biological compatibility. In the most applications, silk fibroin should be dissolved and regenerated. Usually, the regenerated fibroin films were solvable in water. In order to change the regenerated fibroin solvability, the most prevalent method is methanol treatment. However, the films prepared with this method are not suitable for use by themselves and the rudimental methanol has some side effects in biomedical applications. So it is very necessary for us to develop a new method to make no-solvable fibroin films having excellent mechanical properties and avoiding methanol treatment. In this paper, blending degummed silk (2%, w/w)) with concentrated fibroin solution, the no-solvent films was obtained through drying the solution at 40-45°C. The conformation of silk fibroin films was analyzed by infrared spectrum, X-ray diffractometry and Differential scanning calorimetry (DSC). The results demonstrated that the SF mainly showed β -sheet conformation when the degummed silk blended with fibroin, while the pure SF membrane showed α /random coil confromation and β -sheet crystal if the other conditions were same. This suggested that the degummed silk could induce the formation of β -sheet crystal and the no-solvable films, which didn't need after-treatment with methanol, could obtained at approximately room temperature. The tensile strength and breaking elongation of films were 29.8MP and 59.6%, which distinctly superior to the fibroin films treated with methanol. The stability in water of films was excellent and many rob structure appeared in the films.