Evaluation of the electrochemical and antibacterial behavior of calcium-phosphate coating formed by plasma electrolytic oxidation method on pure titanium

The purpose of this research is to investigate the electrochemical and antibacterial behavior of calcium-phosphate coating formed by the plasma electrolytic oxidation (PEO) method using an electrolyte containing Na3PO4.12H2O, KOH, and Ca3(PO4)2 salts on pure titanium. For this purpose, the surface structure of the coating was evaluated by scanning electron microscopic images and its chemical composition by Raman spectroscopic analysis. The electrochemical behavior of the coating was studied in simulating body fluid (SBF) using electrochemical impedance spectroscopy and potentiodynamic polarization tests. The antibacterial behavior of PEO coatings was evaluated under two conditions without irradiation and under ultraviolet radiation and against gram-positive Staphylococcus aureus bacteria. The results showed that the formed PEO coating had a porous structure and included the anatase crystalline phase. After 7 days of exposure of the samples to SBF solution, the values of polarization resistance (Rp) of pure titanium substrate and PEO coating were 0.097 and 0.263 MΩ.cm2 , respectively. Therefore, by modifying the surface of pure titanium with the help of the PEO coating process, its corrosion resistance increased by about 2.7 times. After exposing the PEO coatings to ultraviolet radiation, their antibacterial behavior was improved due to the production of reactive oxygen species (ROS) by the coatings and as a result damage to Deoxyribonucleic acid (DNA), proteins, and other intracellular components and finally the death of bacteria.