Preparation And Application Of Three-dimensional Porous Silk Fibroin/Poly (ε-caprolactone) Nanofibrous Scaffolds

In recent years, more and more researches apply tissue engineering methods to repairtissue defects. As an effective method to fabricate sub-micron, or even nanoscale fibers,electrospinning was widely used in bone tissue engineering. However, traditional electrospunnanofibrous scaffolds couldn’t totally meet the requirements of bone tissue engineering. Sobased on the simulation of natural bone structure, this thesis optimized the structure oftraditional electrospun silk fibroin (SF)/poly(ε-caprolactone)(PCL) nanofibrous scaffold byapplying wet-electrospinning and biomineralization. The biological properties of optimizednanofibrous scaffolds were evaluated, and a core-shell nanofibers drug delivery system basedon the optimized nanofibrous scaffolds was established.Firstly, SF/PCL blend nanofibrous scaffolds with three-dimensional shape and large porestructure were prepared by wet-electrospinning and freeze-drying. Their preparation techniques,morphology, compression performance and pore structure were characterized; the effects ofpre-frozen temperature on pore structure, porosity and compression performance werediscussed. The results indicated that50℃ethanol coagulating bath could improve thecollection of nanofibers and increase silk II crystalline structure of SF. SF/PCL blendnanofibrous scaffolds have three-dimensional shape with pore size of over100μm and porosityof over90%. As the pre-frozen temperature decreased, the pore size decreased, the porosityincreased, while the compression performance increased at first and then decreased.Secondly, the3D SF/PCL blend nanofibrous scaffolds were biomineralized using10timessimulated body fluid (10×SBF). The morphology, structure and mineralized layers werecharacterized; the effect of deposition time on the compression performance was also studied.The results showed that10×SBF could biomineralize the3D SF/PCL blend nanofibrousscaffolds efficiently, and a certain thickness of apatite layer was obtained on the surface ofSF/PCL nanofibers. The apatite layer was a compound of dicalcium phosphate dehydrates (DCPD) and hydroxyapatite (HAP). The compression performance of biomineralized3DSF/PCL blend nanofibrous scaffolds increased with the increment of deposition time.And then, the biological properties of SF/PCL blend nanofibrous scaffolds prepared abovewere evaluated. The results showed that the3D SF/PCL blend nanofibrous scaffolds both withand without biomineralization have good biocompatibility, the adhesion and proliferation ofMC3T3-E1on them were as good as SF/PCL blend nanofibrous membranes. However, theproliferation process of MC3T3-E1on the3D SF/PCL blend nanofibrous scaffolds withbiomineralization was slower than others. Furthermore, the migration depth of MC3T3-E1onboth scaffolds could be at least2.47mm due to the three-dimensional shape and large porestructure.At last, the core (Bovine Serum Albumin, BSA)-shell (SF/PCL) nanofibers drug releasesystem was established based on the3D SF/PCL blend nanofibrous scaffolds. The processconditions of core-shell nanofibers were determined; the drug release properties of this systemwere evaluated using BSA as model drug. The results indicated that the drug release3DSF/PCL blend nanofibrous scaffolds also have3D shape and large pore size; this core-shellnanofiber structure system could slowly release BSA, the drug release mechanism werenon-Fickian diffusion and matrix erosion.