Imaging ROS-induced modifications in living systems 4 5

Significance: Reactive Oxygen Species (ROS) mayregulatesignaling, ion channels, transcription factors and biosynthetic processes. ROS-related diseases can be either due to a shortage or to an excess of ROS. Recent advances: Since biological activity of ROSdepends on not only concentration but also spatial and temporal distribution, real-time imagingof ROS, possibly “invivo”, has be-come a need for scientists,with potential for clinical translation. New imaging techniques, as well as new contrast agents in clinically established modalities, was developed in the last decade. Critical issues: An ideal imaging technique should determine ROS changeswith high spatio-temporal resolution, detectphysiologically relevant variations in ROS concentration and provide specificity towards different redox couples. Furthermore, for invivoapplications, bioavailability of sensors, tissue penetrationand a highsignal-to-noise ratio are additional requirements to be satisfied. Future directions: None of the presented techniques fulfill all requirements for clinical translation. The obvious way forward is to incorporate anatomical and functional imaging into a common hybrid-imaging platform.