Growth of Nanotubular Flowers Using Environment-Friendly Electrolytes and their Biomedical Applications

Abstract

Plasma-induced electrochemical anodization (PA) is introduced as an alternative strategy for fabricating titanium oxide nanostructures using environmentally benign, chloride-based electrolytes. Unlike conventional anodization methods that rely on metallic cathodes and fluoride-containing acidic electrolytes, the PA approach employs an atmospheric-pressure plasma jet (APPJ) as the cathode, enabling anodization in aqueous sodium chloride solutions with optional ethylene glycol addition. By adjusting electrolyte composition and processing conditions, hierarchical flower-like microstructures composed of densely packed nanotube-like TiO2 features were obtained. The most uniform and well-defined structures were obtained with 2.5 M NaCl and ethylene glycol. Additional oxygen plasma treatment modified surface chemistry and enhanced wettability without altering surface morphology. Biological evaluation demonstrated that PA-treated surfaces significantly reduced platelet adhesion and activation, decreased Escherichia coli attachment by up to 92%, and promoted endothelial cell adhesion and spreading. Smooth muscle cells also exhibited increased adhesion to modified surfaces; however, their morphology was altered, with reduced spreading and a nonuniform distribution. Overall, the more pronounced response of endothelial cells indicates a favorable trend toward endothelialisation. These findings demonstrate that plasma-induced electrochemical anodization enables the fabrication of titanium surfaces with multifunctional biological performance, combining reduced thrombogenicity and bacterial adhesion with enhanced endothelial response. The use of fluoride-free electrolytes further highlights the potential of this approach for applications in cardiovascular and other blood-contacting biomedical devices.