Measurement of Singlet-Oxygen In Vivo: Progress and Pitfalls

This article is a highlight of the paper by Jarvi et al. in this issue of Photochemistry and Photobiology as well as a brief overview of the state of the field of singlet-oxygen (O-1(2)) detection in vivo. The in vivo detection of O-1(2) using its characteristic 1270 nm phosphorescence is technically challenging. Nevertheless, substantial progress has been made in this area. Major advances have included the commercial development of photomultiplier tubes sensitive to 1270 nm light, techniques for spatially resolving the location of O-1(2) at a subcellular level and more complex mathematical models for interpreting the kinetics of O-1(2) emission from living cells. It is now recognized that oxygen consumption, photosensitizer bleaching, oxidation of biological molecules and diffusion of O-1(2) can significantly change the kinetics of O-1(2) emission from living cells.