Silk F Ibroin Materials Reinforced By Pva-co-PE Nano Short Fibers

Silk fibroin materials are widely used in the fields of cosmetics,food,and biomedicine due to their natural skin-friendly properties,edible properties,good biocompatibility,biodegradability,and low body inflammatory response.When silk fibroin is used in the field of biomedicine,the mechanical properties of the silk fibroin material cannot always meet the requirements of tissue engineering scaffold materials.Moreover,the traditional silk fibroin material lacks the micro-nano level physical guidance signals required for cells.Therefore,it is of great necessity to introduce micro-nanoscale fibers into silk fibroin to improve its mechanical and biological properties.PVA-co-PE nanofibers can be dispersed in aqueous solution as single short fiber after being mechanically cutting,which provides a theoretical basis for the blending of silk fibroin and PVA-co-PE nanofibers.Firstly,the PVA-co-PE nano-short fiber/silk fibroin blended composite membranes were prepared and characterized by means of SEM,Instron,ATR and XRD.The effects of PVA-co-PE nano-short fiber with different contents on the surface morphology and mechanical properties of the blended composite membrane and its spatial structure after 75% ethanol treatment were studied.The experimental results showed that the top surface of the blended composite film was no longer smooth compared to the pure silk fibroin film.Many bulges appeared due to PVA-co-PE nanofibers encapsulated in silk fibroin,and the under surface was as smooth as pure silk fibroin film.The breaking stress and breaking strain of pure silk fibroin films were 42.00±2.70 MPa and 1.00±0.09% respectively on dry conditions,and the breaking stress and breaking strain of pure silk fibroin films were 2.75±0.39 Mpa and 36.85±9.09% respectively on wet conditions.When 5% PVA-co-PE nanofibers were added,the mechanical properties of the blended composite membranes were improved significantly under dry and wet conditions.The breaking stress and breaking strain of the blended composite membranes on dry conditions reached 59.20±1.60 MPa,1.60±0.03%,respectively,and the breaking stress and breaking strain of the blended composite membranes on dry conditions can reach 3.40±0.37 Mpa and 40.18±7.52% respectively.The secondary structure of the pure silk fibroin film and the blended composite film after 75% ethanol treatment were changed.The treated blended composite membrane was mainly β-sheet structure.Secondly,based on the above two-dimensional materials,the PVA-co-PE nano-short fibers/silk fibroin blend porous scaffold materials with three-dimensional porous structure were prepared.The composite porous scaffolds were characterized by SEM,ATR,XRD and other testing methods.The effect of adding different content of PVA-co-PE nanofibers on the surface morphology and water absorption performance of the blended porous scaffolds was studied,and the changes of the space structure after the soft freezing treatment were carried out.The experimental results showed that the pore diameter of the pure silk fibroin porous scaffold was 50-200 μm and the pore wall surface was smooth.After adding PVA-co-PE nano-short fibers,the pore size of the blended scaffold was significantly reduced to 50-150 μm,and the traces of the nano-short fibers coated in the silk fibroin can be seen,and the more the nano-short fibers were added,the traces were more apparent.The addition of PVA-co-PE nanofibers can significantly improve the swelling ratio performance of the porous scaffolds.With the increase of the nano-short fibers content,the swelling ratio of the blended porous scaffolds was continuously increased.When the content was 50%,the swelling ratio reached 31.29±0.62 times,while the swelling ratio of pure silk fibroin porous scaffold was only 12.27±0.57 times.The soft freezing treatment of silk fibroin can change the secondary structure of silk fibroin,and the molecular conformation of silk fibroin in the composite porous scaffold material was mainly β-sheet structure.Finally,this study investigated the influence of temperature and PVA-co-PE nanofibers on gelling time of mixed hydrogels.The micromorphology and secondary structural changes of the blended hydrogels were characterized by the means of SEM,ATR,and XRD.The experimental results showed that the higher the temperature,the shorter the gel time.After sonication,the pure silk fibroin aqueous solution in a 37°C biochemical incubator changed into hydrogel after 1 hour.PVA-co-PE nanofibers can significantly promote gelation.In the range of 5-20%,the more PVA-co-PE nanofibers,the shorter the gelation time.In addition,PVA-co-PE nanofibers can significantly change the pore size and pore surface morphology of the hybrid hydrogels.When the content was 20%,the mixed hydrogel has the smallest pore size and the pore size was about 10 μm,significantly lower than pure silk fibroin hydrogel pore size.The wall marks can be seen on the walls of the pores due to the coating of nanofibers in silk fibroin,and the more nanofibers,the wall marks was more obvious.