Blood-compatible biomaterials by surface coating with a novel antithrombin-heparin covalent complex

Covalent antithrombin-heparin complex (ATH) was covalently grafted to a pol ycarbonate urethane (Corethane (R)) endoluminal graft (a kind gift of Corvi ta Corporation) after being activated using 0.3% m/m NaOCl in 0.15M phospha te pH 6.0. ATH graft density (1.98 x 10(-7) mol/m(2)) was 6 times the maxim um amount of unfractionated heparin (UFH) that could be bound to polycarbon ate urethane surfaces, Surface-bound ATH could be stored in sterile 0.15M N aCl at 4 degreesC for at least 2 months with good antithrombotic activity b efore being implanted into rabbits. Analysis of ATH-coated tubing showed th at it contained significant direct thrombin inhibitory activity. In vivo te sting in a rabbit model was compared to non-activated non-coated surfaces, activated-non-coated surfaces, hirudin-coated surfaces and antithrombin (AT )-coated surfaces. The weight of the clot generated in the ATH-coated graft tubing was significantly less than the weight of the clot generated within the hirudin-coated graft (p = 0.03 with a 1-tailed Student's t test). The anticoagulant nature of ATH grafts in vivo was shown to be due to bound ATH because both the AT-coated surfaces and non-coated but activated surfaces showed similar thromboresistant efficacy to that of untreated material (ANO VA; p < 0.05). Apart from the direct antithrombin activity that contributed to much of the prolonged patency in vivo, surface-bound ATH likely catalyz ed AT inhibition of thrombin, as evidenced by a significant number of I-125 -AT binding sites (greater than or equal to1.5 x 10(-8) mol/m(2)). Thus, AT H appears to be a good candidate for coating cardiovascular devices, such a s endoluminal grafts, with high levels of substitution and significant long -term blood-compatibility. (C) 2001 Elsevier Science Ltd. All rights reserv ed.