Wettability and In Vitro Bioactivity of Doped TiO2 Nanotubes

With low-modulus alloys of Ti35Nb and Ti35Nb15Zr as the anodization substrates, amorphous TiO2 nanotube arrays doped by Nb and Zr elements were fabricated through a surface anodization method. The wettability and in vitro bioactivity of the doped TiO2 nanotubes and undoped nanotubes were investigated. Experimental results indicated that the existence of Nb and Zr elements in the anodic oxides could refine the diameter of the nanotubes and help to grow longer nanotubes. All of the as-anodized nanotubes demonstrated a hydrophobic behavior, which was different from those of the metallic substrate surface. The wettability of the TiO2-based nanotubes varied with the type of the substrate or dopant element. The doping with Nb element could improve the wetting behavior of the TiO2 nanotubes. And simultaneous doping with Nb and Zr elements could have more significant improvement in the wetting behavior. After immersion in simulated body fluids (SBF) the doped TiO2 nanotubes could induce a quick apatite formation. The Nb/Zr doped nanotubes presented quicker apatite formation rate than the Ti-Nb-O nanotubes did at the initial immersion stage. The above findings make it possible to further control or modify the wettability toward either hydrophobic or hydrophilic surfaces, and explore related biological properties of the doped nanotubes.