Design of a New Near-Infrared Ratiometric Fluorescent Nanoprobe for Real-Time Imaging of Superoxide Anions and Hydroxyl Radicals in Live Cells and in Situ Tracing of the Inflammation Process in Vivo

The superoxide anion (O₂^•–) and hydroxyl radical (^•OH) are important reactive oxygen species (ROS) used as biomarkers in physiological and pathological processes. ROS generation is closely related to the development of a variety of inflammatory diseases. However, the changes of ROS are difficult to ascertain with in situ tracing of the inflammation process by real-time monitoring, owing to the short half-lives of ROS and high tissue autofluorescence in vivo. Here we developed a new near-infrared (NIR) ratiometric fluorescence imaging approach by using a Förster resonance energy transfer (FRET)-based ratiometric fluorescent nanoprobe for real-time monitoring of O₂^•– and ^•OH generation and also by using in situ tracing of the inflammation process in vivo. The proposed nanoprobe was composed of PEG functionalized GQDs as the energy donor connecting to hydroIR783, serving as both the O₂^•–/^•OH recognizing ligand and the energy acceptor. The nanoprobe not only exhibited a fast response to O₂^•– and ^•OH but also presented good biocomapatibility as well as a high photostability and signal-to-noise ratio. We have demonstrated that the proposed NIR ratiometric fluorescent nanoprobe can monitor the changes of O₂^•– and ^•OH in living RAW 264.7 cells via a drug mediating inflammation model and further realized visual monitoring of the change of O₂^•– and ^•OH in mice for in situ tracing of the inflammation process. Our design may provide a new paradigm for long-term and real-time imaging applications for in vivo tracing of the pathological process related to the inflammatory diseases