Preparation Of Silk Fibroin Protein Nanospheres And Its Modification On Regenerated Silk Fibroin Fibers

Bombyx mori silk fibroin(SF)has several kinds of amino acids necessary for the human body,has excellent biological compatibility,is natural and green,safe and non-toxic,so it has been widely used in the fields of tissue engineering and biomedicine in recent years.Among them,silk fibroin microspheres prepared from natural silk fibroin have been paid more attention because of their controllable particle size,suitable for passing through different biological transport barriers,and lower antigenicity than other commonly used biodegradable polymers such as polylactic acid.In this thesis,based on the self-assembly behavior of silk fibroin protein,SF nanospheres were prepared by enzymatic hydrolysis.The effects of the amount of enzyme and the self-assembly time of silk fibroin protein on the morphology,structure and properties of SF nanospheres were studied.In this thesis,a mature wet spinning process was adopted,and two different dissolution systems were used to blend SF nano-spheres with silk fibroin to prepare recycled silk silk.The effects of SF nano-spheres on the morphology,secondary structure and mechanical properties of recycled silk silk were studied.On the basis of blending with SF nano-microspheres to produce regenerated yarn with high mechanical properties,let SF nano-microspheres wrap TiO₂NPs in order to obtain functional regenerated silk with good mechanical properties.Compared with the recycled silk spun by adding nano TiO₂into the spinning solution,the ultraviolet resistance of different recycled silk was compared.The main research contents of this thesis are as follows:1.Preparation of silk fibroin nanospheresIn this experiment,based on the self-assembly behavior of silk fibroin,SF nanospheres were prepared by enzymatic hydrolysis-drying-dissolution method,and the prepared SF nanospheres were characterized by SEM,XRD,FT-IR and Zeta potentiometer,and discussed The effect of the amount of enzyme and the self-assembly time of silk fibroin solution on the morphology,conformation,particle size and crystallization properties of SF nano-microspheres.The results show that by changing the amount of enzymes and the time of self-assembly,the average particle size of SF nanospheres can be effectively controlled;increasing the amount of enzymes will gradually reduce the average particle size of SF nanospheres;increasing the silk fibroin solution The average particle size of SF nanospheres gradually increases with the self-assembly time.2.Formic acid-calcium chloride(FA-CaCl₂)system spinning regenerated silkUsing the mature wet spinning process in our laboratory,SF nanospheres and silk fibroin are blended under the formic acid-calcium chloride dissolution system.When the addition amount of SF nanospheres is 0-30%,the breaking strength of the regenerated yarn shows a trend of increasing first and then decreasing,while the elongation at break continues to decrease.And with the increase of the added concentration,the average diameter of the regenerated silk gradually decreased,from the average diameter of22.44±1.70?m to 12.79±3.36?m.Infrared spectroscopy(FTIR)and X-ray diffraction(XRD)results show that compared with pure regenerated silk fibroin(RSF)fiber,RSF fiber with SF nanospheres contains higher?-sheet structure and greater crystallinity And grain volume.Therefore,although the breaking strength of the regenerated silk after adding SF nanospheres has been improved,the breaking elongation has continued to decrease,which affects its practical application value.3.Lithium bromide(LiBr)system spinning regenerated silkWhen SF nanospheres and silk fibroin are blended in a formic acid-calcium chloride solution system,the mechanical properties of the regenerated silk are not excellent enough,and the continuous decrease in elongation at break makes it difficult to truly use it in real life.Therefore,it is necessary to find a new dissolving system to blend to prepare high-performance regenerated silk.In this experiment,we continued to use the wet spinning process to blend SF nanospheres and silk fibroin in a Li Br dissolving system.Li Br can significantly reduce the molecular weight of silk fibroin,which may enhance the effect of SF nanospheres on the structure of silk fibroin,produce recycled silk with high mechanical properties.The results showed that when the addition amount of SF nanospheres was 0-30%,the breaking strength and breaking elongation of regenerated silk showed a trend of increasing first and then decreasing.Among them,when the addition amount of SF nanospheres is 10%,the mechanical properties of regenerated silk are the best,the breaking strength can reach 608.14±10.45 MPa,and the breaking elongation can reach 102.52±12.96%,which is significantly higher than that of ordinary regenerated silk.(194.20±8.28 MPa and 19.47±5.37%).Scanning electron microscopy(SEM)showed that the addition of SF nanospheres did not significantly change the morphology of regenerated silk.The results of FTIR and XRD showed that SF nanospheres induced the self-assembly process of silk fibroin in solution and promoted silk fibroin.The secondary structure of the protein is transformed from non-returned crimp to?-sheet,and the fiber contains higher crystallinity and smaller crystal grain volume,which improves the breaking strength and elongation of the regenerated silk,and expands the regeneration application range of silk.4.Preparation of SF nanospheres wrapped with TiO₂NPs and preparation of functional regenerated silkTitanium dioxide nanoparticles(TiO₂NPs)are typical nanomaterials,which have excellent electronic conductivity,catalytic performance and UV resistance,and have a wide range of applications in photocatalysis,biomedicine and other fields.In this study,TiO₂particles with an average particle size of 4 nm were used to prepare SF nanospheres wrapped with TiO₂NPs,and TiO₂-SF nanospheres were blended with silk fibroin solution to prepare regenerated silk,which made the regenerated silk have good mechanical properties and a certain degree of UV resistance.Compared with the regenerated silk made by only adding TiO₂NPs,the regenerated silk made by adding TiO₂-SF nanospheres has better mechanical properties and better UV resistance.This means that the method of modifying the regenerated silk after wrapping the nanoparticles with SF nanospheres is feasible,and a functional regenerated silk with high mechanical properties can be obtained.This broadens the application of regenerated silk in smart wear and other fields to a certain extent range.