| Silk fibroin(SF)is a natural protein polymer macromolecule derived from silk,which can be extracted from waste materials produced in silk processing.It has the advantages of molecular chain flexibility,good cell compatibility,degradability and permeability.Dissolving silk fibroin into films,fibers,scaffolds and gels can be widely used in biomedical fields such as immobilized enzyme carriers,biomimetic materials and functional cell culture matrix.Fibroin dissolution is an essential step for the preparation of various regenerated fibroin materials.The existing system of fibroin dissolution has the disadvantages of high salt concentration,excessive degradation of fibroin,toxic solvent and high cost.Therefore,it is necessary to explore an economical solution to dissolve fibroin that is non-toxic and can avoid excessive degradation of fibroin.In addition,silk fibroin films prepared by traditional methods have such problems as large film thickness,low strength,easy swelling and dissolution in water and difficult control of membrane structure in the process of membrane preparation,so it is necessary to adopt a method with simple operation,stable membrane structure and good performance to prepare silk fibroin membranes.Based on this,a solution system with low salt concentration was used in this paper to dissolve silk fibroin.The dissolved silk fibroin solution was prepared by self-assembly method into a silk fibroin membrane with stable structure and good performance.The specific research contents and conclusions are as follows:(1)study on preparation of nano-silk solution.Based on the low concentration of lithium bromide-dissolved by acetone system,studied the dissolution behavior of silk fibroin,in acetone boiling point temperature,using acetone volatile direct preparation ofhigh concentration of regenerated silk fibroin solution,by controlling the dissolution conditions to determine the best solution process: lithium bromide acetone solution concentration 6%,bath ratio of 1:20,melting temperature of 57 ?,dissolution time of12 h,the fibroin solution concentration was 40%.Using scanning electron microscopy(SEM),differential scanning calorimetry(DSC),Fourier transform infrared spectrum(FTIR)and rheological test on the rheological properties of silk dissolving mechanism and silk extract on lowering blood-glucose were characterized by analysis,the results show that in the process of dissolving,acetone solvent volatilization of ion solvation layer in the destruction of incomplete solvated ions and fibroin molecules in the side chain of serine and collaterals glycine hydroxyl interaction make fibroin begins to dissolve,through test observation found that silk fibroin molecules in solution mainly exist in random conformation,eventually lysate of nano-silk fibers.The rheological test of silk fibroin aqueous solution showed that the three concentrations of silk fibroin aqueous solution all showed shear thinning behavior,30% of the silk fibroin aqueous solution showed greater energy storage modulus than loss modulus,which was a viscoelastic solid,and 25% and 20% of the silk fibroin solution showed greater loss modulus than energy storage modulus,which was a viscoelastic liquid.Dissolution of silk fibroin and its mechanism analysis.To lithium bromide-dissolved by acetone system,this paper studied the dissolution behavior of silk fibroin,in acetone boiling point temperature,using acetone volatile direct preparation of high concentration of regenerated silk fibroin solution,by controlling the dissolution conditions to determine the best solution process: lithium bromide acetone solution concentration 6%,bath ratio of 1:20,melting temperature of 57 ?,dissolution time of 12 h,the fibroin solution concentration of 40%(w/w).Using scanning electron microscopy(SEM),differential scanning calorimetry(DSC),Fourier ir transform spectroscopy(FTIR)and rheological test on the rheological properties of silk dissolving mechanism and silk extract on lowering blood-glucose were characterized by analysis,the results show that in the process of dissolving,acetone solvent volatilization of ion solvation layer in the destruction of incomplete solvated ions interact with fibroin chain make fibroin begins to dissolve,through test observation found that fibroin was dissolved in nano size,preparation of regenerated silk fibroin materials have potential.(2)Silk fibroin membrane was prepared by self-assembly.Preparation of fibroin solution will be diluted to a certain concentration,drops in the air-on the interface of different concentrations of ammonium sulfate solution,get the fibroin membraneprepared by self-assembly method,then fibroin and gelatin with different blending proportion,get fibroin gelatin mixture,on the air interface-ammonium sulfate solution,preparation of gelatin blending with sf membranes,membrane formation experienced diffusion,self-assembly and curing three stages,its mechanism of membrane is the use of fibroin solution and ammonium sulfate solution both difference as a driving force to make the surface tension of the silk fibroin molecules spread rapidly on the gas-liquid interface,according to the amphiphilic properties of silk fibroin,The hydrophobic alanine residue and hydrophilic serine residue of the molecular chain segment are rearranged at both ends of the gas-liquid interface to form a variable gelatinous structure.Finally,according to the denatured effect of ammonium sulfate solution on the silk fibroin molecule,the conformation of this gelatinous structure is transformed(solidified)to form a membrane material with stable structure.By analyzing the factors that influence the film the optimum film forming conditions: fibroin solution optimal concentration of 25%,the optimal concentration of 30% ammonium sulfate,fibroin gelatin optimum blending ratio for 10:0,9:1 and speak,so the preparation of the SF100,SF90 and SF80 three fibroin gelatin blend membrane,the multi-layer composite blend membrane,got 2 and 4 layers of fibroin gelatin composite membrane.(3)Study on the structure and properties of silk fibroin membrane.For preparation of gelatin blending with sf membrane by SEM,FTIR,XRD,DSC,UV test,analysis of the surface morphology and internal composition,the study found that fibroin conformation of gelatin blend membrane is given priority to with beta fold,has the advantages of thin,transparent,porous,contact Angle and tensile test showed that the blend membrane of surface contact Angle less than 60 °,the breaking strength of the dry film is about 45 to 60 MPa,wet is 7 to 14 MPa,with good hydrophilic and mechanical properties.The biological properties of the blend membrane were studied by cell culture and in vitro degradation.The results showed that the silk fibroin gelatin blend membrane could promote the growth and proliferation of cells,and the cell survival rate was more than 100%.After 7 days of in vitro degradation,the quality loss of the membrane was more than 20%,showing good biocompatibility and biodegradability.By comparing the properties of the three blends,it is found that the content of gelatin will affect the transmittance,surface morphology,hydrophilicity,mechanical properties and biological properties.SF100 surface is a kind of cellular structure,based on this structure,SF100 has good hydrophilicity and mechanical properties,and add gelatin,hindered the silk fibroin molecules at the gas-liquidinterface self-assembly,SF90 and SF80 surface pore size and porosity were declined,thus had fallen to hydrophilic and mechanical properties,and light transmittance and biological properties are improved.By comparing the properties of monolayer and multilayer,it is found that the surface contact Angle of multilayer is about 70 °,hydrophilicity decreases,and the tensile strength in wet state is more than twice as high as that of monolayer.To sum up,this research adopts the low concentration of lithium bromide-acetone solution system of silk fibroin dissolve,by acetone solvent volatilization damage of salt ions and dissolved silk,by the use of salt reduction and melting temperature is low,reduce the degradation of silk,in the process of dissolving the silk fibroin solution concentration is higher,for in the gas-liquid interface self-assembly into silk fibroin membrane,fibroin membrane thin,transparent,porous,hydrophilic,excellent mechanical properties and biological properties is good,has potential application value in the field of biological engineering. |
PDF Full Text Request