Fabrication of Nanocomposites with High Elasticity and Strength for the Load-Bearing Layer of Small-Diameter Vascular Grafts.pdf

Compliancemismatch of commercially available artificialgrafts,where the artificial graft and the native vessel are subject to differentradial expansions, is a major issue that results in graft occlusionafter implantation. A human artery possesses a nonlinear mechanicalresponse to pulsatile pressure due to its nonlinear viscoelastic nature,which is difficult to replicate in artificial graft fabrication. Here,we fabricated nanocomposites with nonlinear mechanical responses forpotential application as the load-bearing layer of vascular grafts,based on a poly(dimethylsiloxane) (PDMS)-casted nanofibrous film.The nanofibers consisted of a core-sheath structure with aPDMS elastomer reinforced with poly(methyl methacrylate) (PMMA) nanofibersas the sheath and thermoplastic polyurethane (TPU) elastomer as thecore. The surface morphology and chemical composition together withthe crystalline structure of the nanocomposites were characterized,and dynamic mechanical analysis was performed to select the graftwith the most suitable properties as the load-bearing layer of a small-diametervascular graft. The presence of the stiff polymer PMMA and elasticpolymer TPU in the PMMA/PDMS/TPU combination resulted in a delayeddissipation of energy after exposure to a force corresponding to 180mm Hg. Casting the PDMS/PMMA/TPU nanofibrous mat into a nanocompositefilm improved the ultimate tensile strength of PDMS without compromisingits elasticity. The compliance values of the nanocomposites were alsofound to be a close match to those of the greater saphenous vein,demonstrating a great potential of the nanocomposites as the load-bearinglayer in a biostable vascular graft.