A new microporous polyurethane vascular graft prepared by an excimer laser ablation technique

Three types of polyurethane (PU) based tubes (internal diameter, 2 mm; wall thickness, 100 microns) with micropores of well controlled size and arrangement were fabricated using an excimer laser (KrF) ablation technique. The pore size (100 microns) and the longitudinal pore-to-pore distance (200 microns) were constant, and the circumferential pore-to-pore intervals were 60 degrees (type 1), 30 degrees (type 2), and 15 degrees (type 3). The surface of the fabricated tube was photochemically modified with photoreactive gelatin. Scanning electron microscopy showed that pore size and arrangement were precisely controlled as designed, and that a gelatinous layer thoroughly covered the luminal surface. The stiffness parameter (beta), inversely related to compliance, was determined from the change in external diameter against intraluminal pressure. An increase in the number of pores around the circumference decreased the beta value. The type 1 tubes implanted preliminarily in rats for 4 weeks showed good patency (80%). The combination of excimer laser-directed microporing and photochemical surface processing techniques enabled the development of a novel compliant small caliber vascular graft, which is expected to show enhanced transmural tissue ingrowth in vivo.