Enhanced functions of vascular cells on nanostructured Ti for improved stent applications

Vascular tissue possesses numerous nanostructured surface features, but most metallic vascular stents proposed to restore blood flow are smooth at the nanoscale. Thus, the objective of the present study was to determine in vitro vascular cell functions on nanostructured titanium (Ti) compared to conventional commercially pure (c.p.) Ti. Results of this study showed for the first time greater competitive adhesion of endothelial versus vascular smooth muscle cells on nanostructured Ti compared to conventional Ti after 4 hours. Moreover, when cultured separately, increased endothelial and vascular smooth muscle cell density was observed on nanostructured Ti compared to conventional c.p. Ti after 1, 3, and 5 days; endothelial cells formed confluent monolayers before vascular smooth muscle cells on nanostructured Ti. Results also showed greater total amounts of collagen and elastin synthesis by vascular cells when cultured on nanostructured Ti. Since a major mode of failure of conventional vascular stents is the overgrowth of smooth muscle cells compared to endothelial cells, these results suggest that while the functions of both types of vascular cells were promoted on nanostructured c.p. Ti, endothelial cell functions (of particular importance, cell density or confluence) were enhanced over that of vascular smooth muscle cells. Thus, the present in vitro study showed that vascular stents composed of nanometer c.p. Ti particles may invoke advantageous cellular responses for improved stent applications.