Biocompatibility and bio-corrosion resistance of amorphous oxide thin films

The corrosion resistance of biocompatible materials in body fluids is one of the essential factors in the determination of the lifetime of medical implants. Therefore, it is of great relevance to understand the interface processes that occur when a surface is exposed to body fluids. To this end, amorphous titanium and niobium oxide films were deposited on medical grade stainless steel using a magnetron sputtering system. The biocompatibility of the films was evaluated by adhesion and viability/proliferation assays using human cells, showing non-toxic response. The electrochemical response of the films was evaluated by poteontiodynamic polarization and electrochemical impedance spectroscopy (EIS) as a function of time, up to 500 hrs, using three different simulated body fluids; the NaCl solution and Hartman (Ringer's + Lactate) and Gey's (Ringer's + Phosphates + Glucose) solution. The results indicated that the chemical composition of the solution was very important since different electrochemical behavior was observed for each case. For example, NbO x showed a better resistance than the TiO x films in the Hartman's solution but it failed when Gey's solution was used. Meanwhile TiO x showed a well passivated response for both NaCl and Gey's solution.