Advanced Biomaterials for Vascular Grafts

Abstract

Cardiovascular disease accounts for 17.9 million deaths annually, with peripheral arterial disease (PAD) and coronary artery disease (CAD) frequently requiring surgical bypass using vascular grafts. Autologous saphenous vein -- the gold standard conduit -- is unavailable in 20-30% of patients due to prior harvest, varicosity, or inadequate diameter, necessitating synthetic alternatives. Current synthetic grafts (expanded polytetrafluoroethylene, ePTFE; polyethylene terephthalate, Dacron) perform acceptably for large-diameter (>6 mm) aortic and iliac reconstruction but exhibit unacceptable thrombosis and intimal hyperplasia rates in small-diameter (<6 mm) applications, with 5-year patency of only 30-50% for below-knee bypass. This study developed and evaluated five vascular graft configurations -- ePTFE, Dacron, electrospun polycaprolactone (PCL), decellularised human umbilical artery (dHUA), and a proposed triple-layered electrospun graft (TL-Graft) combining a luminal anti-thrombotic poly(carbonate urethane)-heparin layer, a medial electrospun PCL-elastin layer for mechanical compliance, and an adventitial PCL-collagen layer for tissue integration -- in a validated ovine carotid interposition model (n = 30, 4 mm ID, 6-month follow-up). TL-Graft achieved the highest 6-month primary patency (100%, 6/6), significantly outperforming ePTFE (50%, 3/6; p = 0.014) and Dacron (33%, 2/6; p = 0.005). Endothelialisation coverage at 6 months was 92.4 +- 4.8% for TL-Graft versus 34.6 +- 12.8% for ePTFE (p < 0.001). Compliance mismatch -- the primary driver of anastomotic intimal hyperplasia -- was reduced by 78% in TL-Graft (compliance 4.8 +- 0.6 %/100 mmHg) compared to ePTFE (1.2 +- 0.3; native artery reference: 5.4 +- 0.8). These results establish the triple-layered biomimetic graft as a promising small-diameter vascular conduit and provide a systematic framework for evaluating next-generation vascular grafts