A self-aggregated thermally activated delayed fluorescence nanoprobe for HClO imaging and activatable photodynamic therapy.

Hypochlorous acid (HClO/ClO) is a common ROS that exhibits elevated activity levels in cancer cells. In this study, an ClO-triggered TADF probe, PTZ-MNI, was designed based on a naphthalimide core. PTZ-MNI self-assemble in aqueous environments, exhibiting significantly enhanced fluorescence that demonstrated typical aggregation-induced delayed fluorescence (AIDF) characteristics. The probe not only showed high sensitivity to ClO but also exhibited remarkable selectivity over other reactive oxygen species and disturbance. PTZ-MNI displayed TADF characteristic, including sensitivity to oxygen in toluene, insensitivity to oxygen in aggregated states that maintain long fluorescence lifetimes, a vertical conformation, and a minimal ΔE of 0.01 eV. Cell imaging studies showed the probe could trace ClO by red to green fluorescence in HeLa cell. The colocalization analysis indicated its excellent lysosome-targeting specificity. In addition, PTZ-MNI-O, the compound after oxidation, exhibited effective ROS generation ability and significant PDT effect after irradiation. This work provides guidance for the rational design of responsive TADF luminescent materials used in cell imaging and activatable-PDT.