Stereoisomeric Engineering of Aggregation-Induced Emission Photosensitizers towards Fungal Killing

Abstract The human health crisis caused by fungal infection is impending. Photodynamic therapy (PDT) as an alternative antifungal approach has garnered much interest due to its minimal side effects and negligible antifungal drug resistance. Herein, we develop stereoisomeric photosensitizers ((Z)- and (E)-TPE-EPy) by harnessing different spatial configurations of one molecule. They possess aggregation-induced emission characteristics and ROS, viz. 1O2 and O2−• generation capabilities that enable image-guided PDT. Also, the cationization of the photosensitizers realizes targeting of fungal mitochondria for antifungal PDT killing. Particularly, stereoisomeric engineering assisted by supramolecular assembly leads to enhanced fluorescence intensity and ROS generation efficiency of the stereoisomers due to the excited state energy flow from nonradiative decay to the fluorescence pathway and intersystem (ISC) process. As a result, the supramolecular assemblies based on (Z)- and (E)-TPE-EPy show dramatically lowered dark toxicity without sacrificing their significant phototoxicity in the photodynamic antifungal experiments. This study is the first demonstration of stereoisomeric engineering of aggregation-induced emission photosensitizers based on (Z)- and (E)-configurations.