Sustainable plant‐leaf‐derived carbon dots with deep‐red emission enable 1‐min photodynamic therapy of tumors

Abstract Malignant tumors remain a major global health challenge, driving the need for effective and biocompatible therapies. Photodynamic therapy (PDT) offers a promising alternative, yet the clinical application of conventional organic photosensitizers is limited by poor photostability and complex synthesis. In this work, we developed a green solvothermal method to synthesize high‐performance carbon dots (PCDs) from Ligustrum sinense leaves. These zero‐dimensional nanomaterials retain porphyrin‐like structures derived from chlorophyll, after carbonization, display markedly enhanced photoluminescence quantum yields and potent reactive oxygen species (ROS) generation. Density functional theory calculations reveals that a cross‐linking process during synthesis leads to a bridged dimer configuration, which inhibits π‐π stacking and promotes efficient electronic transitions for ROS production. In vitro and in vivo studies confirm the excellent biocompatibility of PCDs and their strong antitumor efficacy via both Type I and Type II PDT mechanisms. In vitro, 660 nm light irradiation for 1 min induced mitochondrial dysfunction and widespread apoptosis in CT26 cells. In vivo, PCD‐mediated PDT effectively suppressed tumor growth after either 1 or 10 min of irradiation, with the longer irradiation producing more pronounced tumor inhibition. Transcriptomic analysis further reveals that PCDs‐based PDT significantly alters apoptosis‐related pathways, including upregulation of Tnfrsf21 and downregulation of Bcl2l1 . This study not only presents a sustainable strategy for converting biomass into high‐value nanomedicines, but also provides an efficient and eco‐friendly photosensitizer for local tumor PDT.