Preparation And Properties Of Three-dimensional Nanofiber Porous Scaffolds

Tissue engineering scaffolds not only provide mechanical support for cell growth,but also provide a suitable microenvironment for cell behavior regulation,extracellular matrix(ECM)production,and tissue reconstruction.Three-dimensional(3D)porous scaffolds constructed by nanofibers can imitate natural ECM structures,which has important research significance and potential application prospects for the development of tissue engineering.As a common method of preparing two-dimensional(2D)nanofiber membranes,electrospinning still faces some challenges in preparing 3D tissue engineering scaffolds.In this study,polylactic acid(PLA)and chitosan(CS)are used as the main raw materials to prepare nanofiber membranes with island-like structure by electrospinning,and then porous 3D nanofiber scaffolds are prepared by freeze-drying.In addition,the scaffolds are compounded with polyvinyl alcohol(PVA)which shows good biocompatibility to further improve the mechanical properties and water absorption of the scaffolds.The main contents of this subject are as follows:1.Based on the principle of phase separation between incompatible components in electrospinning process,the positively charged CS tends to migrate outward in a positive electric field.With the increase of PLA molecular weight,the entanglement between PLA and CS molecular chains becomes more serious,and the migration degree of CS decreases.When the molecular weight of PLA is 105 and the ratio of PLA to CS is 70/30,composite nanofibers with island-like structure are successfully prepared.CS is located on the surface of PLA nanofibers,which improves the hydrophilicity and biocompatibility of PLA nanofibers.Using the composite nanofibers as construction materials,3D nanofiber scaffolds with random and directional channels are prepared by homogeneous dispersion and freeze-drying respectively,and their structures are characterized by scanning electron microscopy(SEM).The scaffolds have high porosity,good water absorption performance,and the wet scaffolds exhibit good compression resilience.Cytotoxicity test and cell culture in vitro(CCK-8 test,ALP test,OCN expression and H&E staining)show that the scaffolds have good biocompatibility,and are more conducive to cell proliferation and differentiation than 2D nanofiber membranes.In addition,the directional channels inside the scaffolds have a certain induction effect on the directional growth of mouse pre-osteoblasts(MC3T3-E1).Subcutaneous transplantation in mice shows that the scaffolds have good biosafety and histocompatibility.2.To further improve the water absorption and mechanical properties of PLA/CS 3D nanofiber scaffolds,different contents of PVA are introduced during the homogenization.When the content of PVA is 10%,the scaffolds show the best comprehensive performance.SEM shows that the scaffolds have obvious qualitative channels.The maximum water absorption of the scaffolds increases from 1500%to 2000%.The wet scaffolds have a maximum compressive strain of 70%at a compression rate of 5 mm/min,and can be compressed repeatedly for 100 cycles with the compressive strain of 50%,which indicates the toughness of the wet scaffolds is greatly improved.Vitro cell culture experiments show that the cell adhesion ability of the scaffolds and the ability of cell arrangement growth are further improved after adding PVA.