The Study Of End-point Immobilization Of Heparin On The Surface Of Small-diameter Vascular Grafts In A Miniature Porcine Model

Part? Preparation of small-diameter polycarbonate urethane vascular graftsObjective: To prepare small-diameter polycarbonate urethane vascular grafts by electrospinning.Methods: Polycarbonate urethanes were dissolved in DMF solution.A low-speed rotating Teflon coated mandrel as the collection device to make small-diameter polycarbonate urethane vascular grafts by electrospinning.The mechanical properties and ultrastructure of the prepared grafts were evaluated.Results: In this study,the wall thickness of the small-diameter polycarbonate urethane vascular graft was 0.39±0.03 mm and the inner diameter was 2.94±0.12 mm.The average fiber diameter of polycarbonate urethane vascular graft was 732±320 nm.The average porosity was 82.8±3.1%.The average elastic modulus of polycarbonate urethane vascular grafts and carotid arteries of minipig were 6.28±0.67 MPa,5.07±0.49 MPa.The average ultimate tensile strength were 7.44±0.96 MPa,8.79±0.44 MPa,respectively(n=6).Conclusion: The small-diameter polycarbonate urethane vascular grafts with high porosity,good mechanical properties and nanofiber structure can be successfully prepared by electrospinning technology.Part? Heparin modification on the surface of small-diameter polycarbonate urethane vascular graftsObjective: To explore a novel method of heparin modification on the surface of small-diameter polycarbonate urethane vascular grafts.Methods: The grafts were treated by plasma technology to create an ultra-thin film of stable primary and secondary amines on the graft surface.Then the grafts were immerged in the heparin solution which was prepared in the cyanoborohydride buffer solution.Heparin was conjugated to the inner and outer surfaces of the small-diameter polycarbonate urethane vascular grafts by end-point immobilization.The quantity and stability of heparin were tested.The mechanical properties of small-diameter polycarbonate urethane vascular grafts before and after heparin modification were compared.Results: The white small-diameter polycarbonate urethane vascular graft turned into pale yellow after the plasma treatment.Heparin conjugated to the polycarbonate urethane vascular grafts had good stability and the average content of heparin was 41±3.6?g/cm3.There was no significant change in mechanical properties before and after heparin modification,P>0.05.Conclusion: The plasma-treated polycarbonate urethane vascular grafts conjugated to heparin via end-point immobilization have good anticoagulant activity and stability.It does not affect their mechanical properties.Part ? The study of heparin-modified small-diameter polycarbonate urethane vascular grafts in a miniature porcine modelObjective: To investigate the remodeling and endothelialization of the small-diameter polycarbonate urethane vascular grafts with anticoagulant activity in a minipig model.Methods: Small-diameter polycarbonate urethane vascular grafts with heparin anticoagulant activity were implanted to the left common carotid arteries in the minipigs by an end-to-end anastomosis.At 4 weeks and 6 weeks after surgery,color doppler ultrasonography was performed to detect the patency rate.The grafts were explanted and stained for HE,Masson,EVG and immunofluorescence for v WF,?-SMA to observe the endothelialization and remodeling.Results: The left common carotid artery graft transplantion models were performed in 6minipigs.3 pigs were followed up for 4 weeks,and the patency rates were 100%(3/3);3pigs were followed up for 6 weeks,and the patency rates were 100%(3/3).HE,Masson,EVG staining showed that cells migrated into the middle part of the graft,and there were more cells in the anastomosis at 4 weeks after implantation.There were more cells migrated into the middle part of the grafts,and there were numerous cells in the anastomosis at 6weeks after surgery.Immunofluorescence of v WF,?-SMA showed that discontinuous positive cells were observed in the middle of grafts at 4 weeks,and lots of cells were observed close to the anastomosis.v WF staining revealed a confluent endothelial monolayer covering the lumen,and more ?-SMA positive cells were observed at 6 weeks in the graft wall.Conclusion: The small-diameter polycarbonate urethane vascular grafts via end-point immobilization have good patency rates in a minipig model during short-term follow-up.