Intracellular Hydrogen Peroxide Detection with Functionalised Nanoelectrodes

Hydrogen peroxide (H2O2) is one of the most important reactive oxygen species, and it is involved in a number of cellular processes ranging from signal transduction to immune defence and oxidative stress. It is of great interest to intracellularly quantify H2O2 to improve the understanding of its role in disease processes. In this study, we present an amperometric nanosensor for the quantification of H2O2 at the single‐cell level. Deposition of the electrocatalyst Prussian Blue on carbon nanoelectrodes enables selective H2O2 reduction at mild potentials. Owing to their small size and needle‐type shape, these nanoelectrodes can penetrate the membrane of single living cells, causing only minimal perturbation. The nanosensors allow for the monitoring of penetration‐induced oxidative outbursts as well as the uptake of H2O2 from the extracellular environment in single murine macrophages.