Tri-layered vascular grafts composed of polycaprolactone, elastin, collagen, and silk: Optimization of graft properties.

The purpose of this study was to create seamless, acellular, small diameter bioresorbable arterial grafts that attempt to mimic the extracellular matrix and mechanical properties of native artery using synthetic and natural polymers. Silk fibroin, collagen, elastin, and polycaprolactone (PCL) were electrospun to create a tri-layered structure for evaluation. Dynamic compliance testing of the electrospun grafts ranged from 0.4-2.5%/100 mmHg, where saphenous vein (1.5%/100 mmHg) falls within this range. Increasing PCL content caused a gradual decrease in medial layer compliance, while changes in PCL, elastin, and silk content in the adventitial layer had varying affects. Mathematical modeling was used to further characterize these results. Burst strength results ranged from 1614-3500 mmHg, where some exceeded the capacity of the pressure regulator. Four week degradation studies demonstrated no significant changes in compliance or burst strength, indicating that these grafts could withstand the initial physiological conditions without risk of degradation. Overall, we were able to manufacture a multi-layered graft that architecturally mimics the native vascular wall and mechanically matches the gold standard of vessel replacement, saphenous vein.