Research On Electrospun Foaming Process For Fabricating Three-dimensional And Shape-controllable Tissue Engineering Scaffolds

Tissue engineering(TE)scaffolds can provide cells with growth and reproduction environment,and induce cells to form tissues with specific geometric shape.It is one of the most important part of TE.The ideal scaffold requires a porous and three-dimensional(3D)structure that provides space for cells' adhesion,proliferation and metabolism in tissues or organs.In this study,a foaming technology for fabricating 3D electrospun nanofibrous TE scaffolds with complex shape was presented.The influence of the related parameters during fabricating 3D scaffolds were studied,and experiments in vitro were carried out as well.The main research contents of this study includes:Firstly,presenting a foaming technology for fabricating 3D electrospun nanofibrous TE scaffolds with complex shape.The manufacturing process was as follows:first,a polycaprolactone(PCL)electrospun membrane covered with sodium borohydride was placed in a printed mold and assembled;then,the assembly was immersed in methanol solution and sodium borohydride reacted with methanol within the membrane driven by capillary force;finally,a 3D scaffold was fabricated under the combined action of the chemical reaction and the constraints of mold.Various shaped scaffolds were fabricated successfully by using different molds,including a hollow cylinder-shaped scaffold,a bone-shaped scaffold,a meniscus-shaped scaffold and a scaffold with the look of a cartoon character named Baymax.Secondly,the influence of process parameters on the foaming process of electrospun membrane was systematically studied in the preparation of three-dimensional scaffolds.A orthogonal experiment with L27(313)table was designed to study the effects of PCL solution,electrospinning voltage,flow rate of syringe pump,distance between collector and electrospinning needle,electrospinning time,and weight of sodium borohydride on foaming effect.The experimental results show that concentration of PCL solution,electrospinning voltage,weight of sodium borohydride and electrospinning time have the most influence on foaming effect.The optimal foaming and electrospinning parameters were as follows:concentration of PCL solution was 8 wt%,electrospinning voltage was 15 kV,flow rate of syringe pump was 4 mL/h,distance between collector and electrospinning needle was 20 cm,electrospinning time was 60 min and weight of sodium borohydride was 5 g.Under the optimum conditions,the height of 3D scaffold was 24 mm.Finally,in vitro cell experiments were carried out for the 3D scaffolds.L929 mouse fibroblasts were cultured to test cytotoxicity,biocompatibility and adhesion ability of 2D scaffold,freely foamed 3D scaffold and controllably foamed 3D.The experimental results showed that the 3D scaffolds fabricated by the proposed method were favorable for cell attachment and growth;cultured cells to seventh days using controllably foamed 3D scaffolds proliferation results showed that the optical density(OD)value is 2.732,increased by 21%over 2D scaffold.Meanwhile,this study proposed a new idea of fabricating "cell-scaffold" composite scaffolds with controllable scaffold shape,cell type and cell position with 3D bioprinting technology.The above achievements obtained in this study have solved the bottleneck problem that the traditional electrospinning methods cannot manufacture 3D electrospun scaffolds with controllable shape.This study provided a new process for fabricating 3D scaffolds in medical researches and clinical applications,and it has broad application prospects.