Study On Fabrication And Performance Of Electrospun Polyurethane Based Small-diameter Artificial Vascular Graft

With the development of tissue engineering, it has become a hot topic to fabricatethe small-diameter blood vessels through electrospinning technology with bothbiocompatibility and appropriate mechanical properties. PU-based small-diametervascular grafts with excellent biocompatibility were fabricated by blending andbi-layering electrospinning technology in this dissertation. Following results wereobtained:1. Hybrid PU/PEG fibrous scaffolds were successfully fabricated by blendingelectrospinning technique. The fiber diameter decreased with the increasing PEGcontent in electrospinning solutions, while the porosity increased. With the increasingPEG content, the surface hydrophilicity of scaffolds improved and the mechanicalproperties also increased because of the plasticizing or hardening effect imparted byPEG composition. The platelet adhesion test showed the adhered amount of plateletdecreased significantly and the hemolysis rate was less than5%, which indicted thehemocompatibility of hybrid PU/PEG scaffolds was obviously improved due to theaddition of PEG. Human umbilical vein endothelial cells (HUVECs) could adhere andproliferate better with the20and30%content of PEG in hybrid scaffolds2. The hybrid PU/PEG tubular scaffold loaded heparin sodium was fabricated byemulsion electrospun technology. The heparin sodium releasing study illustrated a burstrelease at initial24h in vitro and then entered into a stable releasing stage. It could beobserved the releasing amount decrease with the increase in heparin sodium contents.The release profile fitted well with Fickian model indicating the heparin sodium releasefollowed the drug diffusion from the fibrous scaffolds. The platelet adhesion andhemolysis rate results showed anticoagulant properties of scaffolds contacted withplatelet for long time were obviously improved due to the addition of heparin sodium.Compare with the hybrid PU/PEG scaffold, the scaffolds loaded heparin sodium weremore favorable for the attachment and proliferation of HUVECs, while suppressed theattachement and growth of smooth muscle cells (VSMCs).3. Crosslinked PU/PEGMA hydrophilic nanofibrous scaffolds were fabricateddirectly from PU and PEGMA macromonomer solutions by reactive electrospinningmethod. The crosslinked PU/PEGMA (90/10,80/20) uniform fibrous scaffolds were obtained with the average fiber diameter of622±110nm and547±77nm. A smallamount PEGMA could improve the mechanical properties of electrospun PU scaffoldseffectively, while fiber morphology could be preserved well. The surface hydrophilicityof crosslinked hybrid scaffolds could be varied the ratio of PU/PEGMA. Furthermore,the appropriate hydrophilic surface with water contact angle in the range of55-75owasfavorable of improvement the HUVECs adhension and proliferation.4. By bi-layering electrospinning technology, the tubular scaffold composed of apolyurethane fibrous out-layer and a gelatin-heparin sodium fibrous inner-layer wasinitially fabricated. The porosity of fibrous gelatin layer could be closely70%. Thegelatin-heparin sodium inner-layer was crosslinked through glutaraldehyde vapormethods which could decrease the mass loss significantly and preserve the stability ofscaffold. The PU out-layer consisted of uniform fibres with average diameters reached784±312nm, and the size of interconnected pores was almost1.60μm. Themechanical test demonstrated that elastic PU layer could improve the flexibility anddecrease the rigid property of the gelatin layer. The gelatin-based fibrous scaffoldscould support the attachment and proliferation of HUVECs. The platelet and hemolysisrate tests showed the scaffolds possess excellent hemocompatibilty as blood contactingmaterials due to the gradual release of heparin sodium.