Preparation And Application Of Fibrous Silk Hydrogels

Silk fibroin（SF）has good biocompatibility and regeneration processing performance,which was expected to be applied as drug delivery carriers,biological templates and flexible strain sensing sensors.SF hydrogels are usually prepared through chemical crosslinking,whose structure are mainly lamellar and porous.And the brittleness of the material is usually large.These methods have made it difficult to meet the practical application requirements.Therefore,the construction of biocompatible and flexible fibrotic hydrogels by simple and rapid methods has a wide application prospect.In this study,the preparation conditions,physical and chemical characteristics of fibrous hydrogels were discussed and their application fields were analyzed on the basis of the study that the preparation of fibrous hydrogels were controlled by the low-voltage-electrogels method and synergistic induction method of acetic acid-ethanol.Firstly,the morphology transformation and performance change of SF electrogels under low voltage electric field were studied,with effectively through regulating the extra electric field,concentration and pH of SF solution.In the process of electrogelation,low voltage electric field was developed to control the nanofiber network morphology formation and inducing a transition from an overall protein structure that is initially rich in random coil to one that is rich inβ-sheet.Under voltage（3～24 V）,solution concentration（<5 wt%）and neutral,alkaline conditions,SF fibrous electrogels were easily formed.At the same time,the voltage（>25 V）and acidic condition would be favorable for the formation of lamellar structures.Under different external conditions,the porosity of the SF electrogels were generally more than 90%,and the compression stress could reach up to1402±107 kPa when the compression strain was 60%.And the mechanism of drugs release of SF electrogels was mainly driven by Non-Fickian transport.Moreover,the SF electrogels displayed good antibacterial properties against Staphylococcus aureus and Escherichia coli.And in vitro cytotoxicity tested illustrated that the electrogels showed a good biocompatibility with mouse embryonic fibroblasts 3T3 cells.At the same time,about the synergistic induction method of acetic acid-ethanol,the transformation of physical and chemical properties of SF hydrogels were explored by adjusting the concentration of ethanol.Hydrogels showed nanofiber network morphology with 1.09±0.5μm diameter.The compressive stress of SF fibrous hydrogel was 75.16±3.79 kPa at dry state and 7.2±0.3 kPa at wet state.Besides,the hydrogels showed higher drug loading rate and better drug slow-release performance.Secondly,the above SF electrogels were processed into a uniform film at certain pressure.There were three ways that were used to obtain flexible conductive composite films,including SF/CNTs blends,CNTs coating and CNTs/SA/SF electrogels.And the physical strength of the composite membrane was improved.The experimental results showed that the CNTs/SA/SF electrogels membrane had a steady signal transmission and good sensitivity（GF=9.86）under micro strain（10%strain）,and could accurately sense small strain changes by human fingers.It showed certain application potential in the field of flexible strain sensing sensors.Finally,using biomimetic mineralization principle and SF electrogels as a template.Then the crystals of iron oxide（Fe₃O₄）nucleation and growth on the surface of SF electrogels in orientation.The Fe₃O₄ nanoparticles with controllable diameter（200～500nm）and good dispersion were obtained.The saturation magnetization strength could reach56.43 emu g^-1.The coercivity was small,and the nanoparticles had good superparamagnetic properties.Subsequently,PSA/1%Fe₃O₄ magnetic filaments were fabricated by using wet spinning method,and its diameter was 357.88±4.13μm.A large number of uniform microporous structures were distributed inside the filament,and the stress was 26.94±0.22MPa.And the saturation magnetization strength could reach 9.31 emu g^-1.Furthermore,the potential application of magnetic switch and textile molding was explored.