Electrochemical Measurements of Reactive Oxygen and Nitrogen Species inside Single Phagolysosomes of Living Macrophages

The release of reactive oxygen and nitrogen species (ROS/RNS) by macrophages undergoing phagocytosis is crucial for the efficiency of the immune system. In this work, platinized carbon nanoelectrodes were used to detect, characterize, and quantify for the first time the intracellular production rates of the four primary ROS/RNS (i.e., H₂O₂, ONOO^–, NO^•, and NO₂^–) inside single phagolysosomes of living RAW 264.7 murine macrophages stimulated by interferon-γ and lipopolysaccharide (IFN-γ/LPS) to mimic an in vivo inflammatory activation. The time-dependent concentrations of the four primary ROS/RNS in individual phagolysosomes monitored using a four-step chronoamperometric method evidenced a high variability of their production rates. This intrinsic variability unravels the complexity of phagocytosis.