Development and evaluation of a compliant polyurethane, endothelial cell seeded vascular graft for use in infrainguinal arterial bypass

Lower-limb vascular by-pass undertaken with prosthetic graft does not have the longevity associated with use of autologous saphenous vein. This work evaluates a new prostheses made from Chronoflex, a compliant polyurethane (CPU), with regard to its compliance, endothelial cell (EC) seeding, and biostability characteristics. The in vivo compliance range that the Chronoflex CPU graft should simulate was determined in 33 human subjects with and without peripheral vascular disease (PVD). The compliance of the femoropopliteal artery was 2.2 - 14.1% mm Hg-1 x 10-2; PVD was associated with a reduction in compliance. The compliance of grafts made from polytetrafluoroethylene (ePTFE), Dacron and Chronoflex CPU was measured in vitro and compared to human artery and vein. Chronoflex CPU and artery had similar compliance values (mean +/- SD: 8.1 +/- 0.4 and 8.0 +/- 5.9% mm Hg-1 x 10-2 respectively). The requirements for successful EC seeding of the Chronoflex CPU graft were sought by seeding graft segments over a range of concentrations and incubation periods prior to washing, gamma counting and scanning electron microscopy. Densities beyond 18 x 105 cells/cm2 did not result in greater residual cell retention; the saturation density of Chronoflex CPU was found to be 9.65 +/- 1.2 x 105 cells/cm2. Maximal cell retention was observed with 240 minutes incubation. Seeding under these conditions, 72.2 +/- 2.5% of initially attached cells remained adherent following 6 hours of perfusion using a pulsatile flow circuit. Chronoflex CPU grafts, incubated in degenerative media for 70 days and assessed for change by SEM and compliance measurement resisted degradation better than poly (ether) grafts although immersion in t-butyl oxidative solutions caused environmental surface cracking. It is concluded that the new graft is likely to diminish graft-artery compliance mismatch, is suited to EC seeding applications and possesses superior biostability compared to poly (ether) grafts.