Research On The Shear-induced Silk Solutions And The Preparation Of Orientated Hydrogels

Silk fibroin hydrogels have been mainly applied in biomedical and engineering field as a natural biological materials based on their excellent biocompatibility and biodegradablity.In this paper,using silk fibroin as raw materials,and mixing sodium surfactin with the silk fibroin solution as promoting agent to prepare the SF hydrogels under the condition of a certain temperature and shear force.The orientated hydrogels were prepared by controlling the change of shearing rotate speed,concentration of SF and sodium surfactin concentration.Some methods were used to explore its conformation transition and the orientation gel mechanism during gelation,and observe its morphology characteristics,and test its mechanical properties and cell compatibility.Shearing rotate speed can promote silk fibroin solution gelation process.After exerting shear force,the gelation time is greatly shorten,and forming silk fribroin/sodium surfactin blended hydrogels within an hour.At the early stages of the shear,silk fibroin solution presents a large number of random coil or ?-helical conformation.Silk fibroin molecules are typical ?-folding conformation until 60 min.The shear process induced silk fibroin/sodium surfactin hydrogels,the direction parallel to shear stress is obvious orientation fiber structure,and the orientation became more significant with the improvement of shearing process.Under the same shearing rotate speed,the compression mechanical properties of orientated hydrogels are higher than unoriented hydrogels,and the direction parallel to shearing stress is higher than other directions.With the increase of shearing rate,the compression performance of the oriented hydrogels get better.The oriented silk fibroin/sodium surfactin hydrogels have excellent mechanical properties,biodegradable properties,biocompatibility and highly orientation,there is potential application value in cultivating nerve,bone,ligament cells to repair defective tissues and organs.The concentration of silk fibroin has a large effect on the mechanical property of the blended hydrogels.In the condition of the same silk fibroin concentration,the shear-induced silk fibroin/sodium surfactin hydrogels exhibit a significant mechanical compressive strength,compared with the control fibroin/surfactin hydrogels undergoing no shearing process,and the direction parallel to the orientation is larger than any other directions.The higher the concentration,the stronger the mechanical properties of the shear-induced silk fibroin/sodium surfactin gels.The resilience performance is poorer when the concentration is low,with the further increase of concentration,there is no significant discrepancy in elasticity.Furthermore,the cutting strength perpendicular to the orientation is the highest,and there was no remarkable difference in the direction parallel to the orientation and no shearing process.The concentration of sodium surfactin also has a positive effect on the mechanical property of the blended hydrogels.In the same condition of sodium surfactin concentration,the compression strength in the orientation direction and the cutting performance perpendicular to the orientation all are significantly improved after shearing process.As the concentration increases,the compression and cutting performance of the shear-induced hydrogels are improved,and the compression property in orientation direction is superior than the other directions,the cutting performance perpendicular to the orientation is higher than the direction parallel to the orientation.In addition,the compression resilience of the hydrogels by shearing and without shearing process are remarkable,and there is no remarkable variance with the change of the concentration.