Dissolution And Regeneration Of Antheraea Pernyi Silk Fibroin And The Structure And Properties Of Its Silk Protein-Based Materials

Antheraea pernyi silk fibroin(ASF)has been a potential candidate in the application in biomedical filed because of excellent biocompatibility,slow degradability and its inherent RGD tripeptide sequence which is the integration receptor of mammalian cells.However,the Antheraea pernyi fibers are very difficult to dissolve and there is a weakness of mechanical properties in regenerated ASF materials.Therefore,the dissolution,regeneration and mechanical properties of ASF fibers need to be further optimized.On the other hand,the structure and properties could be adjusted by the blending with other materials,which can extend its application as biomaterials.In this study,firstly,in order to obtain a higher molecular weight and enhance the mechanical properties of ASF material,the molecular weight of ASF and mechanical properties of ASF film that gained by dissolving ASF fibers in Ca(NO3)2 solution under different conditions were investigated.The results showed that the dissolution of ASF was closely related to the dissolved temperature and time.The dissolved ability was limited in a lower temperature,and it was very difficult to dissolve Antheraea pernyi fibers when the temperature was below 90?.Whereas if the dissolved temperature was higher and the dissolved time was longer,the damage to silk fibroin molecules was greater and the molecular weight was smaller,too.Further,After different dissolution conditions to get the solution of film,its mechanical strength is different,too.Further,the influence on the strength of different ASF films under different dissolved conditions was discussed.It was found that the ASF films had the best mechanical properties under the 90 ? and 4 h dissolved conditions,in which the average dry and wet breaking strength were 28.1 ± 2.4 MPa and 2.2 ± 0.3MPa,respectively.In this paper,the best dissolved temperature and time were 90 ?and 4 h.Secondly,the gelation behavior of the bombyx mori and Antheraea pernyi blending silk fibroin solution was studied.The results showed that the gelation rate of ASF wasvery fast,it could completely become gelation in 33 min in 37 ?.However,the mechanical properties of ASF hydrogel was much poor,even could not form a gel when the concentration was below 5%.What was worse,the ASF hydrogel was fragile and difficult to maintain a completely shape after lyophilization.On the contrary,the gelation rate of bombyx mori silk fibroin(BSF)was quite slow,and it need about 7days to form a gel in 37 ?.Gel dynamics tests showed that the gelation rate of the ASF/BSF blending solution could be controlled by adjusting the blending ratio.The gelation rate gradually accelerated with the increasing of ASF content,and the mechanical properties of hydrogel increased with the increasing of BSF content.Again,the structure and properties of ASF/BSF blending films were investigated.The results demonstrated that the secondary structure of different proportion of the blending ASF/BSF films mainly were random coil and it also exist a small amount of?-sheet,and after the ethanol treatment,the molecular conformation mainly was?-sheet.For the mechanical properties,the breaking strength and elongation of the blending films increased with the increasing of bombyx mori silk fibroin,especially when the amount of BSF increased to 50%,the mechanical properties had significantly enhanced.the breaking strength and elongation were 41.34 Mpa,1.37%,respectively.Further,the degradation behavior of ASF,BSF and its blending film was researched,it was found that the loss mass of ASF film was more and the degradation rate in protein enzyme XIV was more faster,after 21 day degradation,the residual rate was only 46.4% left,while there was 77.0% left of BSF film,and the50ASF/50 BSF blending film had a degradative residual rate of 62.3%.The degradation rate can be adjusted by the change of blending ratio of ASF and BSF.The research results in this paper showed that the mechanical properties and degradation rate of silk fibroin films can be regulated in a certain range by changing the blending rate of ASF and BSF.Finally,the structure and mechanical properties of ASF/BSF blending films by the addition of graphene oxide(GO)was preliminary studied.It was found that the addition of GO had no significant influence on the structure of ASF/BSF blending film.However,if the content of GO was too high or too low,it will cause the loss ofstrength and can obviously reduce its breaking strength and elongation.This may be related to the impact that GO had on the intermolecular force and crystallization structure and the existence of separation between GO and ASF.By the study of this paper,the dissolved conditions had a great impact on the molecular weight of ASF.The molecular weight of ASF can be improved and the mechanical properties of its materials can be increased by the adjustment of dissolved condition.At the same time,the gelation rate,degradation rate and mechanical properties of silk fibroin can be effectively adjusted by the adjustment of ASF/BSF ratio,which provided a new idea and way to control the properties of silk fibroin biomaterials.Though there was no obvious influence on the structure of ASF/BSF blending films with the addition of GO,it had significant impact on the mechanical properties.