Research On The Structural Transformation Of Regenerated Silk Fibroin

Researchers at home and abroad had studied the effects ofγ-ray irradiation, ultrasonic, polyalcohol and shear stress on the structural transformation of regenerated Bombyx mori silk fibroin, to a certain extent. But so far, the research on the structural transformation of regenerated Antheraea yamamai, Antheraea perny silk fibroin by these factors has been very rare. In this paper, we have focused on the effects ofγ-ray irradiation, ultrasonic, polyalcohol and shear stress on the structural transformation of regenerate Antheraea yamamai, Antheraea perny silk fibroin, compared with the behavior of Bombyx mori silk fibroin affected by these factors, further to discuss the formation mechanism of silk fibroin gel.The structural transformation of silk fibroin molecules in the regenerated Antheraea yamamai, Antheraea perny, Bombyx mori silk fibroin films with different doses ofγ-ray radiation treatment was studied by analyzing the experiments of X-ray diffraction, FTIR spectroscopy, Differential Scanning Calorimetry and Mechanical Properties Test. The results showed that there were not noticeable changes in the crystal structure and molecular conformation of those silk fibroin films. However, with the increase in radiation dose, the thermal stability of those silk fibroin films becomes a slight weaker, the broken strength and the broken elongation rate of those silk fibroin films decreased greatly.The effects of ultrasonic on the structural transformation of the regenerated Antheraea yamamai, Antheraea perny, Bombyx mori silk fibroin molecules were studied. The gelation time of the silk fibroin solution was determined and the structure of silk fibroin gels was analyzed by X-ray diffraction and FTIR spectroscopy. The results show that when the power was lower than 400 W, with the increase of ultrasonic power, the gelation time of Antheraea yamama silk fibroin solution decreased gradually, and when the ultrasonic power was higher than 400W, as the ultrasonic power increased, the gelation time raised slightly. When the power was lower than 500 W, with the increase of ultrasonic power, the gelation time of Antheraea perny silk fibroin solution decreased gradually. And when the ultrasonic power was higher than 500W, as the ultrasonic power increased, the gelation time also raised sharply. As the ultrasonic power increased, the gelation time of Bombyx mori silk fibroin solution decreased sharply. The ultrasonic can accelerate the gelation of silk fibroin solution and promote the structural transformation of silk fibroin molecules from random coil orα-helix toβ-sheet, but the crystal structure and molecular conformation of silk fibroin gels are not significant.The effects of polyalcohol (EG, PEG600) on the structural transformation of the regenerated Antheraea yamamai, Antheraea perny, Bombyx mori silk fibroin molecules were studied. The gelation time of the silk fibroin solution was determined and the structure of silk fibroin gels was analyzed by X-ray diffraction, FTIR spectroscopy, Raman spectroscopy, Scanning electron microscopy. The results show that when the adding percentage is less than 300%, either EG or PEG600, with the increase in the adding percentage of polyalcohol, the gelation time of the Antheraea yamamai or Antheraea perny silk fibroin solution decreased sharply, and when the adding percentage is more than 300%, with the increase in the adding percentage, the gelation time raised slightly. The gelation time of the Bombyx mori silk fibroin solution dropped sharply with the increase in the adding percentage. Polyalcohol can accelerate the gelation of silk fibroin solution and promote the structural transformation of silk fibroin molecules from random coil orα-helix toβ-sheet, but the crystal structure and molecular conformation of silk fibroin gels are not significant by the polyalcohol. When the adding percentage of EG was 300%, the silk fibroin gel has relatively uniform pores.The effects of shearing force on the structural transformation of the regenerated Antheraea yamamai, Antheraea perny, Bombyx mori silk fibroin molecules were studied by X-ray diffraction, FTIR spectroscopy and Circular Dichrosim, and the gelation time of the silk fibroin solution was determined. The results show that the gelation time of the Antheraea yamamai or Antheraea perny silk fibroin solution decrease sharply with the increase in the shearing time. When the shearing time is less than 45 min, the gelation time of Bombyx mori silk fibroin solution decreases slightly with the increase in the shearing time, but when the shearing time is more than 45 min, the gelation time dropped sharply. The longer the shearing time or the bigger the shear rate or the longer the positioned time, the bigger the percentage ofβ-sheet silk fibroin in solution. Shearing force can accelerate the gelation process of silk fibroin solution and promote the structural transformation of silk fibroin molecules from random coil orα-helix toβ-sheet, but the crystal structure and molecular conformation of silk fibroin gels are not significant.In summary, silk fibroin films withγ-ray irradiation treatment have no changes in the molecular conformation and crystal structure, but the mechanical properties of those films become weaker. Ultrasonic, polyalcohol and shearing force can accelerate the gelation of silk fibroin solution and promote the structural transformation of silk fibroin molecules from random coil orα-helix toβ-sheet, but the crystal structure and molecular conformation of silk fibroin gels are not significant changed. The formation of silk fibroin gels mainly contains aβ-sheet process of silk fibroin molecules.