A Ru/RuO(2)-Doped TiO(2) Nanotubes as pH Sensors for Biomedical Applications: The Effect of the Amount and Oxidation of Deposited Ru on the Electrochemical Response

In the field of orthopedic or dental implants, titanium and its alloys are most commonly used because of their excellent mechanical and corrosion properties and good biocompatibility. After implantation into the patient’s body, there is a high risk of developing bacterial inflammation, which negatively affects the surrounding tissues and the implant itself. Early detection of inflammation could be done with a pH sensor. In this work, pH-sensitive systems based on TiO(2)-Ru and TiO(2)-RuO(2) combinations were fabricated and investigated. As a base material, Ti-6Al-4V alloy nanostructured by anodic oxidation was used. Ruthenium was successfully deposited on nanotubular TiO(2) using cyclic polarization, galvanostatic and potentiostatic mode. Potentiostatic mode proved to be the most suitable. The selected samples were oxidized by cyclic polarization to form a TiO(2)-RuO(2) system. The success of the oxidation was confirmed by XPS analysis. The electrochemical response of the systems to pH change was measured in saline solution using different techniques. The measurement of open circuit potential showed that unoxidized samples (TiO(2)-Ru) exhibited sub-Nernstian behavior (39.2 and 35.8 mV/pH). The oxidized sample (TiO(2)-RuO(2)) containing the highest amount of Ru exhibited super-Nernstian behavior (67.3 mV/pH). The Mott–Schottky analysis proved to be the best method. The use of the electrochemical impedance method can also be considered, provided that greater stability of the samples is achieved.