An Electrochemical Biosensor with Dual Signal Outputs for Ratiometric Monitoring the Levels of H₂O₂ and pH in the Microdialysates from a Rat Brain

The serious damage of ischemia to brain function has attracted extensive attention. As two of vital signal molecules, development of biosensors for monitoring of hydrogen peroxide (H₂O₂) and pH in vivo is significant to understand the roles of H₂O₂ and pH playing in rat brain followed by ischemia. Herein, a selective and accuracy ratiometric electrochemical biosensor was developed for quantifying H₂O₂ and pH through both current and potential outputs in a rat brain upon ischemia. Catalase (Cat) was first employed as a specific recognition element for both H₂O₂ and pH. Meanwhile, an inner reference molecule, ferrocene (Fc), independent of H₂O₂ and pH, was used as a built-in correction to improve the accuracy. The reduction peak current of Cat increased with increasing concentration of H₂O₂ from 1.0 to 230 μM. Meanwhile, the peak potential negatively shifted with increasing pH from 5.91 to 7.81, resulting in determination of H₂O₂ and pH. Thus, combined with the remarkable analytical performance of the developed biosensor and the desirable biocompatibility of carbon fibre microelectrode (CFME), a direct and reliable approach was established to monitoring H₂O₂ and pH in the microdialysates collected from rat brain followed by cerebral ischemia.