Mark T. Ehrensberger

Cathodic electrical stimulation has been investigated as a way to treat implant‐associated infection of orthopaedic devices. One of the proposed mechanisms of these effects is the changes in chemical gradients adjacent to the implant generated by the cathodic reaction products. Of these reaction products, both alkaline pH and hydrogen peroxide have been implicated as antimicrobial agents. However, direct measurement of these chemical effects has yet to be fully characterized for orthopaedic biomaterials. Microelectrodes are powerful tools that can be used to measure localized chemical conditions. Most commercially available sensors are fabricated from pulled glass pipettes, which make them quite fragile. In order to more easily make measurements of the effects of electrical stimulation, more durable sensors are desired. Solid‐state electrodes were fabricated from platinum and iridium micro‐wires to make H₂O₂ and pH‐sensitive electrodes, respectively. Additionally, a similar method was used to fabricate electrodes that were housed within a stainless steel needle, which could be used to penetrate and measure in solid samples without damaging the sensor. The H₂O₂ microelectrode was found to have a sensitivity of 34.1 pA/µM and a R² value of .996. The pH microelectrode was found to have a linear calibration from 2 to 12 with a sensitivity of 76.7 mV/pH and a R² of .996. The needle‐based electrodes were found to be able to detect changes in both H₂O₂ and pH when tested in an agar gel model.

Osseointegrated (OI) prosthetic limbs have been shown to provide an advantageous treatment option for amputees. In order for the OI prosthesis to be successful, the titanium implant must rapidly achieve and maintain proper integration with the bone tissue and remain free of infection. Electrochemical methods can be utilized to control and/or monitor the interfacial microenvironment where the titanium implant interacts with the biological system (host bone tissue or bacteria). This review will summarize the current understanding of how electrochemical modalities can influence bone tissue and bacteria with specific emphasis on applications where the metallic prosthesis itself can be utilized directly as a stimulating electrode for enhanced osseointegration and infection control. In addition, a summary of electrochemical impedance sensing techniques that could be used to potentially assess osseointegration and infection status of the metallic prosthesis is presented.

Three Mg alloys, Mg–1.34% Ca–3% Zn (MCZ), Mg–1.34% Ca–3% Zn–0.2% Sr (MCZS), and Mg–2% Sr (MS), were examined to understand their bio-corrosion behavior. Electrochemical impedance spectroscopy and polarization scans were performed after 6 days of immersion in cell culture medium, and ion release and changes in media pH were tracked over a 28 day time period. Scanning electron microscopy (SEM) of alloy microstructure was performed to help interpret the results of the electrochemical testing. Results indicate that corrosion resistance of the alloys is as follows: MCZ > MCZS > MS.