Covalently-attached heparin multilayer coatings on the luminal surface of silicone-coated vascular graft

The microporous expanded polytetrafluoroethylene (ePTFE) vascular grafts were coated using silicone as a soft support by flowing through the lumen of the graft, followed by post-coating with a second thin film consisting of Nafion. The sulfonic head groups within pendant chains of Nafion created "anchor" sites for the formation of additional multilayers of a photosensitive crosslinker amine polymer (PA) and heparin (Hep) via electrostatic interaction on the Nafion coatings. After drying, multilayers of PA/Hep were then fixed by a covalent bonding via photoreaction between heparin and the crosslinker without compromising its catalytic capacity to promote antithrombin III-mediated thrombin inactivation. Compared with ionically attached multilayers of PA/Hep, the stability of the covalently attached PA/Hep was improved greatly. The technique is robust, cheap and environmentally friendly. Thus, photocrosslinking heparin multilayers appear to be a good candidate for coating medical devices of almost any kind and any shape.