Mitochondria-targeted pentacyclic triterpenoid carbon dots for selective cancer cell destruction via inducing autophagy, apoptosis, as well as ferroptosis

Natural products have been an important database for anti-cancer drug development. However, low water solubility and poor biocompatibility limit the efficacy of natural products. Carbon dots (CDs), as an emerging 0D material, have unique properties in bioimaging, water solubility and biocompatibility. Here, we prepared three pentacyclic triterpenoids (PTs) included glycyrrhetinic acid (GA), ursolic acid (UA) and oleanolic acid (OA), which have anticancer activity but poor water solubility, as raw materials into CDs to improve disadvantages. Our data indicated that the active surface groups of all three CDs were largely preserved and were able to excite green fluorescence. Their carboxyl edges not only exhibited excellent water solubility, but also specifically targeted tumor cell mitochondria due to high sensitivity to ROS-induced damage and high internal oxidative stress. In cancer cells, the PT-CDs induced cell death through three pathways (apoptosis, ferroptosis, and autophagy), which is essentially the same way their raw materials induce death, but the effect was much stronger than raw materials. Notably, functionalized PT-CDs also exhibited extremely low toxicity. In summary, PT-CDs not only have improved water solubility and biocompatibility, but also retain the structure of their raw materials well and exert better efficacy, which provides new ideas for the development of anti-cancer natural product drugs.