The first water-soluble NIR AIEgen was synthesized and used for ultrafast wash-free cellular imaging and photodynamic cancer cell ablation.

Efficient organic photosensitizers (PSs) have attracted much attention because of their promising applications in photodynamic therapy (PDT). However, guidelines on their molecular design are rarely reported. In this work, a series of PSs are designed and synthesized based on a triphenylamine-azafluorenone core. Their structure−property-application relationships are systematically studied. Cationization is an effective strategy to enhance the PDT efficiency of PSs by targeting mitochondria. From the molecularly dispersed state to the aggregate state, the fluorescence and the reactive oxygen species generation efficiency of PSs with aggregation-induced emission (AIE) increase due to the restriction of the intramolecular motions and enhancement of intersystem crossing. Cationized mitochondrion-targeting PSs show higher PDT efficiency than that of nonionized ones targeting lipid droplets. The ability of AIE PSs to kill cancer cells can be further enhanced by combination of PDT with radiotherapy. Such results should trigger research enthusiasm for designing and synthesizing AIE PSs with better PDT efficiency and properties.

The enzymatic antioxidant system (EAS) protects aerobic cells from oxidative stress. However, it is brittle and susceptible of inactivation of reactive oxygen species (ROS) immoderate production. Here, we demonstrated that MoS nanosheets (few-layer MoS), as a multifunctional nanozyme, possess intrinsic activity of mimicking enzymes of superoxide dismutases (SODs), catalases (CATs), and peroxidases (PODs) under physiological conditions (pH 7.4, 25 °C). Further, MoS nanosheets showed POD-like activity by transferring electrons instead of generating ROS. Similar to EAS, a defense termed nanozymatic antioxidant system (NAS) was developed by MoS nanosheets, for regulation of oxidative stress. Surprisingly, this NAS can effectively scavenge other free radicals including hydroxyl radicals (OH), nitrogen-centered free radicals (DPPH), and nitric oxide (NO). To evaluate these unique properties of MoS-based NAS in vivo, Escherichia coli ( E. coli), Staphylococcus aureus ( S. aureus), and A549 cell models were established, respectively. These results showed MoS nanosheets superiorly protect bacteria and cells against oxidative injury caused by HO. This work makes MoS nanosheets promising antioxidants in the pathological processes and expands their application in biocatalysis and nano-biomedicine.