Preparation And Properties Of Silk Fibroin Porous Scaffolds With Nanofibrous-like Component

With the further investigations of tissue regeneration, cells proliferation in 3D scaffolds in vitro, researchers gradually discovered that a qualified tissue engineering scaffold , besides impressive biocompatibility and biodegradability, needs to satisfy basic parameters such as appropriate porous structures and nanofibrous architecture that is similar to the nano-fibrillar structure of extracellular matrix (ECM), which is favorable for inducing cell adhesion, proliferation, migration and differentiation, thus achieving the goal of reconstruction and regenerationthe for damaged tissues and organs.In the present research, nanofibrous architecture is processed through controlling silk protein molecules self-assembly, and its impact on pore structure of silk fibroin scaffold prepared by freeze-drying. We regulated the secondary structure of scaffolds by adding glycerin and water annealing and explored the effects of glycerin content to the enzymatic degradation performance of scaffolds. In addition, we also studied influence of Nanofibrous silk fibroin porous scaffolds on the proliferation and differentiation of SD rats mesenchymal stem cells.The silk fibroin solution was treated by slowly concentrating at 60℃. The AFM results showed that silk fibroin molecules formed nanofiberous-like structure by self-assembly. Silk fibroin solution, before and after slowly drying treatment, was made into scaffolds by freeze-drying respectively. SEM,X-ray diffraction and FTIR spectroscopy results indicated that nanofiberous structure made scaffolds present a relatively perfect round pores.Scaffolds was prepared by adding different ratios of glycerol in the slowly concentrating process (ratios of silk fibroin and glycerol in the dry state of 100:0,100:20,100:40,100:60 and100:80, respectively). X-ray diffraction, FTIR spectroscopy, DSC and TGA curve analysis showed that conformation transformed into silk I in the ratios of silk fibroin and glycerol in the dry state of 100:20. With the increase of glycerin content, silk fibroin crystal structure shifted from silk I to silk II , and thermal stability enhanced. The higher the glycerin content, the slower the degradation rate of scaffolds in XIV protease. In enzymatic degradation process,α-helix and the random structure decreased whileβ-sheet content increased. Silk porous materials were treated with water annealing for different time. X-ray diffraction, FTIR spectroscopy, DSC and TGA curve analysis showed that water annealing processing made silk fibroin form a lot of silk I structure. The longer water annealing time, the higher the crystallinity and stability in water.In order to clarify the influence of different scaffolds on cells growth and proliferation, (SD) rats mesenchymal stem cells were cultured on silk fibroin scaffolds prepared by means of freeze-drying with different glycerol content, vacuum vapor and salt-leaching. The laser confocal microscope and DNA content assay showed that cell proliferation was better on scaffolds prepared by slowly drying than those prepared by salt-leaching. This was related to nanofiberous structure in silk fibroin scaffolds.This paper provided a method to prepare scaffolds containing nano fibers with controllable pore size and secondary structure under an all-aqueous process and without toxic chemical reagents and organic solvents. It is expected to provide a new optional scaffold of excellent properties for tissue engineering and tissue induction.