Microporous small diameter PVDF-TrFE vascular grafts fabricated by a spray phase inversion technique

Microporous polyurethane vascular prostheses fabricated by phase inversion show good patency and excellent endothelialization in the rat aona replacement model. Grafts with a negative electric charge on the luminal surface may show less early thrombosis than neutral materials. To test that hypothesis microporous prostheses, 1.5 mm ID, 15-22 mm long, were fabricated with a polyvinilidene fluoride· trifluoroethylene (PVDF·TrFE) copolymer by the spray, phase inversion technique. Some of the grafts were made piezoelectric by poling under a high electrical field . Overall 24 poled grafts (P) and 24 unpoled grafts (UP) were implanted in the infrarenal aona of 48 adult rats. There was no significant difference in patency berween the two types of grafts. Both showed similar macroscopic and microscopic findings. At 2 days, fibrin deposition was somewhat heavier on the poled grafts, but no difference in surface platelet deposition could be detected . Endothelialization was observed from both anastomoses at 2 weeks and was almost complete at 6 months. The excellent biocompatibility and the microporous structure of the grafts were probably the dominant factors in the success with these grafts. Although piezoelectric activity remained measurable in excised, cleaned prostheses, the charges developed may have been too small to exert a biological effect either because of insufficient dipole orientation or inadequate mechanical deformation.