Research Of Surface Modified Moderate-Caliber Dacron Vascular Graft Via Layer-by-layer Assembly Of Heparin And Chitosan

The requirements of Moderate-Caliber Dacron Vascular Graft have been manifolded throughout these years,due to the increasing morbidity and mortality of atherosclerotic diseases.The major vascular grafts applied in the clinical pracice have two kinds:1) autologous vessels,such as radial artery,internal mammary artery,and saphenous vein, which was restricted by the limited source;2) synthetic grafts,such as expanded polytetrafluorethylene(ePTFE) and Polyethylene terephthalate(Dacron or PET) grafts, which are the most widely used in the clinical use.Thus,surface modification of synthetic vascular grafts to improve the short-term and long-term patency is the one of the most pratical methods in the present situation.In this study,we get the moderate-caliber Dacron vascular graft surface modified via layer-by-layer assembly of heparin/chitosan,and study the biocompatibility and mechanical properties according to the GB standards.After that, we evaluate he modified vascular grafts in the animal experiments by the means of B-ultrasonograft,MRA,scanning electron microscope,histochemistry and immunohistology.PartⅠThe biocompatible tests of the heparin/chitosan modified Dacron vascular graftObjective:preparation and biocompatible evaluation of the heparin/chitosan modified Dacron vascular grafts.Methods:preparation of the heparin/chitosan modified Dacron vascular grafts by layer-by-layer assembly.Evaluation of the biocompatibility of the modified grafts according to the GB/T 16886.4 and ISO 10993-4,GB/T 16886.5 and ISO 10993-5,cell adhesion,MTS assay,LDH release assay,acute toxicity tests,subcutaneous implantation,direct hemolysis, indirect hemolysis,and boold platelet adhesion tests.Results:The micro-structure of the modified grafts maintained after the layer-by-layer assembly.Good cell adhesion of the modified Dacron grafts approved by the cell strain of ECV304 and fibroblast L929.The modified grafts were innoxious in the cytotoxity tests by the MTS assay and LDH release tests(P＞0.05);No significant difference was found both in the acute toxicity test and the inflammation the modified grafts after subcutaneous implantation comparing to the negative control.The red blood cell destruction was found in the direct and indirect hemolytic tests.The anticoagulate effects of the modified grafts were better than the unmodified grafts.Conclusion:The Dacron vascular grafts could be modified by the layer-by-layer assembly of heparin/chitosan,and the modified grafts maintain good biocompatibility.PartⅡMechanical properties of the heparin/chitosan modified vascular graftObjective:Evaluation of the mechanical properties of the heparin/chitosan modified vascular graft.Methods:The wall thickness,inner diameter,diameter under pressure,axial extends intensity,max suture intension,anastomosis explodes pressure,porosity,integral water permeability was examined according to industry standards.(YY 0500-2004)Results:Mechanical properties of the heparin/chitosan modified vascular graft met the standards of the YY 0500-2004 in the wall thickness,inner diameter,diameter under pressure,axial extend intensity,max suture intension,anastomosis explode pressure, porosity,integral water permeability.Concluation:Mechanical properties of the heparin/chitosan modified vascular graft did not undermined in the layer-by-layer assembly,and met the national standards YY 0500-2004.PartⅢThe animal experiment of the heparin/chitosan modified Dacron vascular graftObjective:Evaluation of the heparin/chitosan modified Dacron vascular graft in the animal experiments.Methods:12 beagles were devided into 2 groups,in which modified vascular grafts and unmodified vascular grafts with the length of 6 cm,was implanted in the beageles abdominal aortic artery.Histology,immunohistochemistry,MRA and ultrasonography was examined 4 weeks and 12 weeks after operation.Results:Six heparin/chitosan modified vascular grafts maintain the patency after 4w and 12w;one of unmodified grafts in the control group clogged in the forth month.The histology showed that endothelialization of the modified grafts was completed in 4 weeks after operation.Conclusion:The endothelialization was not disturbed by the heparin/chitosan modified Dacron vascular grafts,and the well patency of short-term and medium-term was found in the modified grafts.