Small-caliber expanded poly(tetrafluoroethylene) vascular prosthesis impregnated with heparin and polyvinyl alcohol gel

Background: Thrombus formation and neointimal hyperplasia still limit the use of small-caliber expanded poly(tetrafluoroethylene) (ePTFE) vascular prosthesis with a diameter less than 6 mm for revascularization in the coronary or peripheral circulation. Bioactive surface heparin coating is one conceivable path for above-mentioned problems. Objective: To elevate the anticoagulant property of ePTFE, this study promoted the patency of a novel small-caliber ePTFE vascular graft by modifying its luminal surface with covalently crosslinked poly(vinyl alcohol)/ p-diazonium diphenyl amine polymer/heparin gel (PVA/PA/Hep gel) and examined the hemocompatibility of the graft. Design, time and setting: Observational experiments were performed at the Nanomedicine and Biosensor Lab, Biomedical Engineering Center, Harbin Institute of Technology from May 2006 to June 2007. Materials: The ePTFE vascular grafts (diameter of 4 mm), Nafion (Naf) and Poly(vinyl alcohol) (Aldrich, USA), heparin (Mw 12 000-14 000) (Calbiochem, USA), p-diazonium diphenyl amine polymer (PA) (this lab, China) were used in this study. Methods: 1 The vascular graft surface was firstly modified with Nafion. 2 Following the impregnation of the mixture of PVA/PA/Hep, covalent crosslinking between polyvinyl alcohol and heparin was performed using crosslinker PA under ultraviolet radiation. Main outcome measures: 1 Contact angles, 2 Attenuated total reflection-fourier transform infrared spectroscopy (ATR-FTIR), 3 Activated partial thromboplastin time (APTT) and prothrombin time (PT), 4 hemolysis test, 5 platelet adhesion test and 6 thrombosin inactivation test. Results: 1 The water contact angle of the vascular graft surface was greatly decreased after modifying. ATR-FTIR revealed the disappearance of diazonium groups at 2 172 cm^-1 and 2 224 cm^-1. Vascular prosthesis after modifying had prolonged APTT and PT, low percent hemolysis and low amount of platelet adhesion. Modified vascular prosthesis had inhibitory effect on thrombosin activity and good coating stability. Conclusion: Converage of PVA/PA/Hep has good antithrombotic function and low percent hemolysis, resulting in improving hemocompatibility of vascular prosthesis.