Development of durable microelectrodes for the detection of hydrogen peroxide and pH

Abstract

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.