Reactive oxygen species (ROS) are involved in numerous physiological processes. At low concentrations, they play a critical role in regulating various biological activities as signaling molecules. Immune cells also produce large quantities of ROS to kill pathogenic microorganisms internalized through phagocytosis. However, abnormal production or accumulation of ROS leads to oxidative stress, which can cause damage associated with aging, cancer, and several neurodegenerative diseases, such as Alzheimer’s and Parkinson’s diseases.

Quantifying ROS, especially inside the phagosome, presents a significant technical challenge due to its highly aggressive internal chemical environment. This challenge is exemplified by the detection and measurement biases observed in vitro, particularly in vesicles surrounded by a lipid bilayer [Serfaty2020].

We contribute to the development and characterization of new ROS detectors, particularly those based on fluorescent proteins. We identified mCherry as a potential H2O2 sensor [Nault2016]. Detection strategies depend on the site of ROS production and the quantity produced [Erard2018].

Our focus has also been on quantifying ROS production in the phagosome, where both the kinetics and amplitude of their generation remain poorly understood. Our method, which labels yeast with DCFH2, is compatible with high-resolution microscopy in highly mobile compartments like phagosomes, where ROS concentrations are high, and the pH is low [Dupré-Crochet2019].