The structure and mechanical properties of A. yamamai, A. perny and B. mori silk fibroin films irradiated by gamma ray with various doses of 0, 25, 50, 100 and 200 kGy, respectively were determined by XRD, FT-IR, DSC and Instron 3365 equipment. Results showed that the aggregation structure and molecular conformation of A. yamamai, A. perny and B. mori silk fibroin films irradiated by gamma ray with those doses mentioned above were not significantly changed. However, with the increase of radiation intensity, the thermal stability of silk fibroin films declined slightly, and the breaking strength and extensibility reduced significantly, due to the breakdown of parts of secondary bonds and covalent bonds. These results suggested that, when these silk fibroin materials were sterilized by gamma irradiation, smaller radiation doses should be used, otherwise irreversible damages on these materials would be caused.

Silk fibroin hydrogels is an important morphous of biomaterial. As a natural protein collosol, purified native silk fibroin solution can be gelatinized under certain conditions. The main mechanism of the gelation is that the fibroin molecules turn into the β-sheet conformation from the random coils. This transformation of silk fibroin molecules would be influenced by various parameters such as the temperature, pH value, ion concentration and so on. In this paper, the effect of ultrasonication on the gelation velocity and structure of silk fibroin were discussed. It is believed that the cavitations caused by sonication could accelerate the process of gelation of silk fibroin. Our experiments demonstrated that the ultrasonic treatment could greatly reduce the silk fibroin gelation time, especially at a high sonication power exceeding 400W. The results of XRD, FTIR, and Raman spectra indicated that the ultrasonication had no significant effect on the final structure and composition of the silk fibroin gels except the acceleration for the molecular transition from random coil and α-structure to β-sheet conformation of silk fibroin. The SEM images showed freeze-dried fibroin gels close to the ultrasonication source had compact structure, while the structure was more loosening far away to the source.

TheBombyx morisilk fibroin microspheres with controllable size were prepared by electrostatic spraying and freeze-drying method. The effects of solution concentration, voltage and flow rate on the sphere size were discussed. The morphology of microspheres was observed by scanning electron microscopy (SEM). The influence of ethanol treatment on the molecular conformation of silk fibroin microspheres was investigated by XRD and FT-IR spectra. The results indicated that the silk fibroin microspheres with diameter in range of 117-363 μm were spherical in shape, and there were plenty of pores both on the surface and in the interior of the microspheres. The sphere size increased with the rising of silk fibroin solution concentration and flow rate, while decreased as the voltage enhanced. The conformation of silk fibroin microspheres changed from random coil to silk II structure after ethanol treatment.

Silk fibroin （SF） hydrogels of the wild silkworm species Antheraea pernyi and Antheraea yamamai were obtained from aqueous SF solutions at room temperature. Both A. pernyi and A. yamamai solutions were slow to gelate. Hydrogels of the two species of wild silkworm were obtained rapidly following ultrasonicaton at 400–500 W. The secondary structure of the freeze-dried SF hydrogels was measured by X-ray diffraction and Fourier transform infrared spectroscopy. Ultrasonication did not change the main secondary structure of the hydrogels, but it accelerated the structural transformation of silk fibroin molecules from random coil or α helix to β sheet and reduced the gelation time.

As the tissue engineering scaffolds, the pore structure and condensed structure of silk fibroin scaffolds should be adjusted and controlled. In this study, Antheraea pernyi/Bombyx mori (A. p/B. m) silk fibroin blend scaffolds were prepared by freeze-drying. The influence of blend ratios on the pore structure and condensed structure of the scaffolds was investigated. The results showed that the average pore diameter of the blend scaffolds changed from 56 to 326 μm. Due to the difference of properties and the macromolecules aggregation status of two silk fibroin solutions, the pore diameter, content of α-helix and crystallinity of the scaffolds decreased with the increasing of the proportion of B. m silk fibroin. By adjusting the blend ratios, the pore structure and condensed structure of A. p/B. m silk fibroin blend scaffolds could be controlled.