Recent advances in hydrogen peroxide imaging for biological applications

Mounting evidence supports the role of hydrogen peroxide (H₂O₂) in physiological signaling as well as pathological conditions. However, the subtleties of peroxide-mediated signaling are not well understood, in part because the generation, degradation, and diffusion of H₂O₂ are highly volatile within different cellular compartments. Therefore, the direct measurement of H₂O₂ in living specimens is critically important. Fluorescent probes that can detect small changes in H₂O₂ levels within relevant cellular compartments are important tools to study the spatial dynamics of H₂O₂. To achieve temporal resolution, the probes must also be photostable enough to allow multiple readings over time without loss of signal. Traditional fluorescent redox sensitive probes that have been commonly used for the detection of H₂O₂ tend to react with a wide variety of reactive oxygen species (ROS) and often suffer from photostablilty issues. Recently, new classes of H₂O₂ probes have been designed to detect H₂O₂ with high selectivity. Advances in H₂O₂ measurement have enabled biomedical scientists to study H₂O₂ biology at a level of precision previously unachievable. In addition, new imaging techniques such as two-photon microscopy (TPM) have been employed for H₂O₂ detection, which permit real-time measurements of H₂O₂in vivo. This review focuses on recent advances in H₂O₂ probe development and optical imaging technologies that have been developed for biomedical applications.