Study On The Assembly And Regulation Mechanism Of Silk Fibroin Nanostructure Under The Solution System

Silk formed under mild conditions has superior strength and excellent toughness. Withthe development of technology, silk has been transformed from traditional textile materialsinto the high-performance materials and showed promising application prospects inmaterialogy, medicine, optics and electronics. More and more researches reaveal that thecomprehensive performance ties to the nano-assembly structures of silk. Therefore, furtherinvestigations into regulating the nanostructure assembly are beneficial to expand thescope of application in the aboved fields for silk fibroin.In order to illustrate the assembling and controlling mechanism of the silk sibroinnanostructure, we firstly study the silk fibroin nanostructure in vivo. On the base of thisresults, we slowly concentrated the regenerated silk fibroin aqueous solution to stimulatethe formation process of silk fibroin in the gland. We discuss the assemble process of silkfibroin nanostructure and accompanied by changes in crystal structure, and exploratoryresearch its controlling factors. Subsequently, we continue to engage on the controllingmechanism of charge on the silk fibroin assemble process. Finally, we prepare the silkfibroin materials with excellent properties under this theory instruction.Throuth the study on the the silk fibroin nanostructures in the gland of fifth instarsilkworm with different growth stages, we found that the assemble process from silkfibroin nanoparticles to nanofibers were existed in vivo. In the assemble process, first silkfibroin assembled into nanoparticles, followed by formation of short nanofibrils and finallyshort fibers with length of about300nm before spinning. According to the experimentalresults in vivo, we further simulated the forming process of silk fibroin in vitro to achievethe reconstruction of nanoparticles into the nanofibrils. Through analyzing thenanostructure and secondary structural changes in the process, we found that the assembledprocess was not only a thermodynamic process, but also affected by different dynamicfactors such as the charge, concentration, hydrophilic interaction, and molecular mobility. Specially, further research on the regulation function of the charge in the silk fibroinassembled process revealed that charge distribution played a key role in inducting theinterconversion of the different nanostructures. Eventually, silk fibroin materials withexcellent flexibility in the dry state with oriented nanofibers were successfully prepared byslow drying process.This result proved the possibility of controlling the properties of silkmaterials by adjusting the silk nanostructure and secondary structure.This paper expounds the change process of the silk fibroin nanostructure in vivo andexplores the assembly and regulation mechanism of silk fibroin nanostructure in vitro.Furtherly, on this basis, the silk fibroin materials with outstanding flexibility have beensuccessfully prepared. Overall, this paper which studies the controlling mechanism of silknanostructure assembly will enrich the silk fibroin self-assemble mechanism to someextent and shall provide theoretical support for the design of multifunctional silk basedmaterials applied to the area of tissue engineering, drug release, electrics andoptoelectronics information.