Effect of cathodic polarization on the microenvironment surrounding commercially pure titanium
Clark, Caelen M.
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Periprosthetic joint infection (PJI) is a serious complication associated with joint arthroplasty. The application of Cathodic Voltage-Controlled Electrical Stimulation (CVCES) to commercially pure titanium (cpTi) has previously been shown to have promise as a treatment method for orthopedic implant associated biofilm infections. The charge transfer reactions that result from applying a cathodic polarization to cpTi are thought to be antimicrobial factors associated with this process. The reduction of oxygen and water in solution consumes oxygen and produces hydroxyl ions, as well as reactive oxygen species (ROS) intermediates. In this work, Scanning Electrochemical Microscopy (SECM) techniques were utilized to spatially determine how 1 hour cathodic stimulations affect the oxygen concentration, pH, and ROS in simulated physiological solutions. Voltages of -1.0V, -1.5V, and -1.8V (vs Ag/AgCl) were found to significantly reduce the oxygen concentration in all solutions within 200μm from the surface compared to no applied polarization. In unbuffered saline, the pH showed a voltage dependent increase during a 1 hour polarization. A -1.0V stimulation increased the pH to ~8.88 and a -1.5V stimulation increased the pH to ~10.6. In Phosphate Buffered Saline, the pH was not affected by a -1.0V stimulation, but a small local pH increase was achieved for a -1.5V stimulation. ROS detection was unreliably achieved using an approach profile technique and not achieved by a linear sweep voltammetry technique. This work was able to show that CVCES of cpTi has a large impact on the local oxygen concentration in simulated physiological solutions. The pH of the solutions was increased in a solution and voltage dependent manner. Further experiments are needed to determine the extent of ROS production during CVCES. Overall, CVCES was found to cause oxygen depletion, increased pH and possibly ROS generation in the microenvironment surrounding cpTi, all of which could contribute to the antimicrobial effects associated with this treatment.