A feasible molecular engineering for bright Π-conjugation free radical photosensitizers with aggregation-induced emission

Fluorescence imaging-guided tumor photodynamic therapy (PDT) has received increasing attention due to its higher resolution of fluorescence imaging and noninvasive treatment of PDT. Two problems of fluorescence aggregation-caused quenching (ACQ) and tumor microenvironment hypoxia are urgently resolved in traditional PDT with fluorescence imaging function, but there is still a lack of effective molecular engineering to design delicate photosensitizers (PSs) to overcome fluorescence ACQ and tumor hypoxia, simultaneously. Herein, we develop a feasible molecular engineering to design aggregation-induced emission (AIE)-active PSs with unique free radical (type I) reactive oxygen species (ROS) by researching molecular structure-property relationship, which possesses bright fluorescence at aggregation and low O2-dependent under the process of generating free radical ROS. The intersystem crossing (ISC) channel is activated when frequently enhance intramolecular charge transfer (ICT) effect in electron-rich AIEgens with typical heavy atoms, which ensure enough triplet energy generation to induce superoxide anion free radical (O2−·) generation. In vitro fluorescence imaging and photo triggering biotoxicity evaluation both revealed that new AIE-active photogenerator is a promising candidate for fluorescence imaging-guided PDT.