Study On Design And Fabrication Methods Of Vascular Scaffold With The Characteristics Of Diploic Vein

In the field of tissue engineering,there remains a problem that cells can not penetrate into the scaffold and hinder tissue regeneration.One of the reasons is that there is no vascular structure in the scaffold.Therefore,the design of scaffold with vascular structure,namely,the vascular scaffold,is a key content of tissue engineering.To solve this problem,this study attempted to explore the design,fabrication and in vitro experiment of vascular scaffold with the characteristics of diploic vein.(1)Study on the characteristics of diploic vein.First of all,two skull samples were scanned by micro-CT to reconstruct the 3D skull model.Then,the morphological repair and 3D region growth algorithm were employed to isolate the diploic vein from the skull model,and the topology and local characteristics of the diploic vein were extracted,thus providing the application basis for the design of vascular scaffold.(2)Study on the design method of vascular scaffold.Two scaffold design methods were proposed in the present study,which were mosaic and bifurcated structures.The mosaic vascular scaffold was constructed by layer iteration on the basis of the definitions of mosaic structure,centerline model and surface sweep model.The bifurcated vascular scaffold was constructed by iteration through the definitions of bifurcated unite,vascular path and taper model.In addition,fluid-solid coupling analysis was carried out on the scaffold,proving the effectiveness of the two design methods.These two design methods were universal,which could be applied to other vascular structures.(3)Development of the 3D bio-printer.Based on the extrusion process,a MEP-23 D bio-printer equipped with the high and normal temperature extrusion devices was designed.The high temperature extrusion device adopted the parameters of screw,particle feeding and four zones temperature control,which precisely controlled the material melting process,with the extruded minimum wire diameter of 0.1 mm.The normal temperature extrusion device extruded materials by piston,with the minimum wire diameter of 0.16 mm,which satisfied the accuracy requirements of vascular scaffold with three-level characteristics.Moreover,this 3D bio-printer also provides experimental platform for the fabrication of vascular scaffold.(4)Study on the fabrication of vascular scaffold.Sodium alginate(SA)and acrylamide(AAm)were used as the main components of the vascular scaffold matrix,while isomaltol served as the core material,and the mosaic vascular scaffold was fabricated by processes of vascular core preparation,vascular core embedding,matrix curing and surface modification.Besides,the bifurcated vascular scaffold was fabricated by the processes of mold preparation,material casting,scaffold fitting and coating.Scaffold retention analysis was conducted,verifying that the two fabrication processes successfully prepared the desirable vascular scaffold.(5)Cell culture experiment.To verify the biocompatibility,human umbilical vein endothelial cells(HUVECs)were implanted into the vascular scaffolds for static culture.According to simulation analysis and dynamic perfusion experiment,the HUVECs were subjected to tensile deformation under shear stress,and such deformation increased with the extension of perfusion time,which was conducive to the formation of compliant blood vessels and promoted the vascularization process.Results in this study validate the reasonability of the design method and fabrication process of vascular scaffold.