A theoretical approach to synthetic vascular graft design: surface micro-topography optimization for promoting the retention of endothelial cells

Abstract

The failure of synthetic vascular grafts due to de-endothelialization of the lumen as a result of exposure to fluid-induced shear stress prevents the widespread use of such grafts as small-diameter vessel replacements. Physical surface modification, an approach that seeks to alter the topography of the luminal surface, has been investigated as a method of reducing de-endothelialization under physiological stresses. Based on prior experimental evidence supporting this approach, computation fluid dynamics was used to investigate the impact of selected channel geometry parameters (wall angle, channel width, depth, and radius of curvature) on fluid flow and the resulting wall shear stress. Optimization of these parameters was performed in order to determine if micro-topographical modification of the lumen wall could alter fluid flow in a manner such that favorable conditions for both endothelial cell retention and stimulation are produced. It was found that a 50% decrease in the wall angle, width, and depth causes a decrease in maximum wall shear stress of around 8%, 8%, and 15%, respectively. Additionally, increasing the radius of curvature at the top and bottom edges by 50% results in a 10% decrease in maximum wall shear stress. These results indicate that it may be possible to tune the lumen micro-topography in order to provide a desired range of stresses, and subsequently reduce thrombogenicity by enhancing endothelial cell retention and function.