Greater endothelial cell responses on submicron and nanometer rough titanium surfaces

Abstract

An in vitro competitive coculture system was designed in this study to investigate vascular cell functions on submicron (lateral feature sizes larger than 100 nm) and nanometer (lateral and vertical feature sizes smaller than 50 nm) rough titanium surface features created via e-beam evaporation with identical chemistry to that of control (unmodified) titanium. Rat aortic endothelial cells (RAEC) and rat aortic smooth muscle cells (RASMC) were individually cultured and cocultured on such substrates for 4 h as well as 1, 3, and 5 days. In addition, RAEC and RASMC intracellular collagen and elastin synthesis were determined for up to 14 days on the various substrates. Compared to control flat titanium surfaces, the results showed for the first time that submicron rough surface features on titanium enhanced RAEC proliferation (followed by nanometer surface features), while simultaneously inhibiting RASMC proliferation. In addition, protein synthesis assays demonstrated enhanced collagen and elastin production by RAEC cultured on submicron rough titanium substrates (followed by nano rough) compared to control flat titanium substrates. Surface characterization results showed that submicron rough featured titanium possessed the greatest hydrophilicity (followed by nanometer surface featured), which may have promoted select protein adsorption to increase RAEC over RASMC function. In contrast to RASMC, RAEC morphology was significantly altered by the underlying titanium surface features, which may also explain the altered vascular cell functions on the different substrates. Thus, this study suggested that submicron to nanometer rough surface features should be further studied for improving titanium for vascular stent applications.