Electrochemical hydrogen peroxide sensors fabricated using cytochrome c immobilized on macroelectrodes and ultramicroelectrodes

We report the design and fabrication of hydrogen peroxide (H₂O₂) sensors using heme proteins immobilized on macroelectrodes and ultramicroelectrodes (UMEs). In this sensor design, the heme centers are directly "wired" to the electrode via the use of an imidazole-terminated self-assembled monolayer. We have systematically evaluated the effect of electrode type and size on sensor performance. The limit of detection for H₂O₂ determined using a 10-μm gold UME is significantly lower than that obtained using a stationary macroelectrode. Our results also highlight the advantages of using UMEs for enzyme kinetics analysis; the K_m determined using a 10-μm UME is similar to that obtained from a rotating disk electrode.