Developing a novel benzothiazole-based red-emitting probe for intravital imaging of superoxide anion

Superoxide anion (O-2(center dot-)), the first generated reactive oxygen species (ROS), is a critical player in cellular signaling network and redox homeostasis. Imaging of O-2(center dot-), particularly in vivo, is of concern for further understanding its roles in pathophysiological and pharmacological events. Herein, we designed a novel probe, (E)-4-(5-(2-(benzo[d]thiazol-2-yl)-2-cyanovinyl)furan-2-yl)phenyl trifluoromethane-sulfonate (BFTF), by modifying hydroxyphenyl benzothiazole (a widely used dye scaffold) which includes insertion of both an acrylonitrile unit and a furan ring to extend the total pi-conjugation system and to enhance push-pull intramolecular charge transfer process, and utilization of trifluoromethanesulfonate as the response unit. Toward O-2(center dot-), the probe features near-infrared fluorescent emission (685 nm), large Stokes shift (135 nm), and deep tissue penetration (300 mu m). With its help, we successfully mapped preferential generation of O-2(center dot-) in HepG2 cells over L02 cells, as well as in A549 over BEAS-2B cells by beta-lapachone (an anticancer agent that generates O-2(center dot-)), and more importantly, visualized overproduction of O-2(center dot-) in living mice with liver injury induced by acetaminophen (a well-known analgesic and antipyretic drug).