Antithrombotic Mechanisms of Urokinase lmmobilized Polyurethane

Abstract

SummaryUrokinase immobilized polymer is highly antithrombotic, which cannot be explained only by fibrinolysis. We immobllized 10 IU/cm2 of urokinase to polyurethane by using maleic anhydride methylvinyl ether copolymer as a carrier. Then we incubated blood in circular tubes made of this material, measured the clotting factors and observed the surface of the tubes after incubation by scanning electronmicroscopy and immunofluorescence microscopy. After 5 min incubation, the relative activities of factors V, VIII, IX, X and XII, fibrinogeil, plasminogen and α2 plasmin inhibitor decreased, but the activity of factor VII increased. No platelet adhesion to the surface of the urokinase immobilized polyurethane was observed and there was no significant adsorption of serum proteins, including fibrinogen, fibronectin and vWF antigen, or the surface. Urokinase-immobilized polyurethane catalyzed the digestion of clotting factors as well as fibrinolysis and also inhibited platelet adhesion on its surface probably by inhibiting protein adsorption and its clinical application including vessel prosthesis should be developed further.

Expression of fibrinolysis activators and their inhibitor in neointima of polyester vascular grafts

“…Other important factors, which play a role in graft patency maintenance, are fibrinolysis system components [18,[20][21][22]25,33]. Our results demonstrated increasing intensity of t-PA and u-PA expression with the time following prosthesis implantation.…”

“…Furthermore it is significantly higher than in the corresponding layer of arteries [5,18] and its impairment may contribute to early graft thrombosis [19]. Plasminogen activators increase fibrinolytic potential of the biomaterial luminal surface and predispose to graft patency maintenance [20][21][22]. Whereas the graft failure is associated wit an up-regulation of PAI-1, which results in reduced total fibrinolytic potential of the graft [23][24][25].…”

Small diameter Polyurethane vascular graft reinforced by elastic weft-knitted tubular fabric of polyester/spandex

“…However, graft thrombosis is still a serious clinical problem in spite of continuous improvements in graft development [14]. Polyurethane has been used to solve the thrombus problem due to its excellent elasticity and biocompatibility, and a microporous structure can be successfully fabricated in the wall using different methods [15][16][17][18][19][20][21][22]. The porosity of commercially available polyester (Dacron) knitted vascular grafts can be reduced by coating or sealing with a novel ionic urethane, to improve their blood-proof property.…”

Mechanical properties of small‐diameter polyurethane vascular grafts reinforced by weft‐knitted tubular fabric

“…However, graft thrombosis is still a serious clinical problem in spite of continuous improvements in grafts and vascular surgery 14. Polyurethane appears to be a satisfactory material to solve the thrombus problem due to its excellent elastic property and the biocompatibility, microporous structure can be successfully fabricated in the wall of the vascular grafts using different methods 15–22. Porosity in the vascular grafts wall can be reduced by coating or sealing with a novel ionic urethane, to improve their blood leakproof property.…”