Titanium dioxide nanotubes/calcium silicate composite coatings prepared by alternative loop immersion method

Titania nanotube arrays (TNTs) using self-ordering electrochemical anodization have attracted considerable attention for the development of advanced implants in bone therapies. In this study, titania nanotubes/calcium silicate coating on titanium (Ti) was prepared by a two-step procedure involving the fabrication of TNTs arrays by electrochemical anodization of Ti followed by the formation of CaSiO3 coating over the TNTs by a simple process called “alternative loop immersion method (ALIM)”. To study the effect of ALIM, TNT arrays with different crystal structures were produced by repeated cycles of soaking and zinc (Zn) doping. The results showed that the amount of CaSiO3 deposited increased with the number of immersion treatments. The ability of CaSiO3 to induce the formation of apatite layer was excellent and more significant in the case of ALIM treated amorphous TNTs compared to that of anatase TNTs. Moreover, Zn doped CaSiO3 prepared by adding a certain concentration of zinc nitrate into the soaking system exhibited higher chemical stability and enhanced antibacterial activity. In consideration of the potential clinical applications, in vitro bioactivity was confirmed for the TNTs/CaSiO3 composite by simulated body fluid test, and the result showed that CaSiO3 coating significantly enhanced the apatite-forming ability of TNT arrays.