A Primary Study Of Biomimetic Spider Silk Using Tussah Silk Fibroin As A Model

Animals silks,especially spider silk attract considerable interestbecause of their excellent comprehensive mechanicalproperties.However, the applications of spider silk are restricted becauseof the difficulty in harvest nature spider silk.Therefore,people expect toobtain artificial spider silk fibers that have similar performance as naturalspider silk by mimicing the spin process of silkworm or spider.Biomimetic spin process of spider and Bombyx mori silkworm hasbecome one of hot points.Up to now, most of the research on animal silks focus on spider silkand Bombyx mori silk,recently, it is found that tussah silk has similarprotein compose and amino alignment to spider silk. 90 percents of tussahsilk in the world was produced in China, Since there is still not enoughspider protein that can be offered to study spinning process, tussah silkwas taken as a raw material in this paper. To demonstrate the effect of the spinning velocity on the structureand properities of tussah silk, the mechanical properties and structure oftussah silk rolled from the tussah at different speeds were studied byusing Instron testing machine,IR spectroscope,optical polarizingmicroscope and scanning electron microscope. The results showed thatin certain range of speed, the tenacity, initial modulus,orientation degreeand crystallinity of tussah silk were increased with the increasing speed.To obtain concentrated regenerated tussah silk aqueous solution,the effect of the deguming reagents, its concentration,deguming time anddeguming temperature on the deguming rate was studied.The resultshowed that Na₂CO₃ was the best kind of deguming reagent and thedeguming process is as follows:firstly 5g Na₂CO₃ was dissolved in 1000ml water, then tussah silk was boiled in the water solution for threetimes,the bath ratio of tussah silk to Na₂CO₃ aqueous solution was1:100.Every time the tussah silk was boiled for 45 minutes.The tussahsilk was washed with waterand then dried at room temperature for 24hours.To choose a suitable solvent for degumed tussah silk, degumedtussah silk could be dissolved in many solvent systems,in this paper,Ca（NO₃）₂-H₂O system and LiSCN-H₂O system were chosen. Dissolutionof degumed tussah silk fibers was carried out in Ca（NO₃）₂-H₂O solutionand LiSCN-H₂O solution with various dissolving conditions.It is found the solubility was significantly dependent on the concentration ofsolvents,dissolving temperature and dissolving time.The properconditions of dissolving were selected.Then the silk fibroin solution insolvent were dialyzed against de-ionized water in regenerated cellulosemembrane.In this work the regenerated tussah silk fibroin（RTSF） aqueoussolutions with high silk fibroin content were first prepared and thestability of RTSF aqueous solutions with different concentrations underdifferent temperatures was studied. It was found that thestability ofsolution decreases quickly with the increase of RTSF concentration andtemperature. The solution turns to be gelation gradually when the RTSFconcentration and temperature keep increasing. Some of silk fibroin isturned intoβ-sheet conformation. The above results imply that the RTSFaqueous solution is an unstable system and it should be stored under lowtemperature and only can be concentrated just before processing.The rheological behaviors of concentrated RTSF aqueous solutionswere studied by using a HAAKE RS 150 rheometer. The results show thatthe viscosity of concentrated RTSF aqueous solution is not very high.The rheological behaviors of the regenerated silk fibroin solutions areaffected not only by the RTSF concentration, but also by other factorssuch as the temperature, shear stress, metal ion, the value of PH and so on.In order to prepare spinnable regenerated tussah silk fibroin aqueous solutions, the coordinative effect of various factors on solution should befurther studied.