AIEgen-Terminated Charge-Switchable Zwitterionic Azo Polymer for Tumor Hypoxia Imaging

For fluorescent probes, getting over the obstacles encountered in an organism is an important prerequisite. A zwitterionic to cationic polymer is an attractive approach to realize long-term circulation and high cellular uptake efficiency at the same time. Here, we reported a hypoxia-activatable zwitterionic to cationic azo polymer for tumor imaging, which was composed of an AIEgen-decorated RAFT agent and an azo monomer unit with a carbonate linkage. The zwitterion group endowed it with great anti-fouling property, avoiding being captured by proteins in the blood stream. Under the hypoxic microenvironment, the azo bond was broken and changed into amine with positive charge, which enhanced the cellular uptake efficiency. Meanwhile, the fluorescence quenching effect was cut off because of the destruction of the azo units. Therefore, the probe achieved a “turn-on” process and could be used as a fluorescent probe for tumor hypoxia imaging.