Red-Emissive Ruthenium-Containing Carbon Dots for Bioimaging and Photodynamic Cancer Therapy

Carbon dots (CDs) as an emerging type of carbon nanomaterials exhibit great potential in bioimaging applications owing to their superior optical properties and excellent biocompatibility. However, it is still challenging to fabricate sole carbon dots with integrated functionalities of diagnostic and therapeutic modalities. Herein, we developed a facile strategy to prepare the ruthenium-containing carbon dots (Ru-CDs) via a hydrothermal method using the 5-amino-1,10-phenanthroline ruthenium(II) complex (Ru-Aphen) and citric acid as starting materials. The structure and morphology of Ru-CDs were verified by transmission electron spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and Fourier transform infrared spectra. The Ru-CDs exhibited good water solubility, intense red emission, and efficient reactive oxygen species (ROS) generation. The MTT assay against HeLa cells demonstrated favorable biocompatibility and distinct photodynamic effect of Ru-CDs. Owing to strong luminescence in water (QY = 20.79%) and efficient ROS generation, Ru-CDs were not only applied as bioimaging agents for tumor cells and zebrafish embryos, but also as photodynamic nanoagents for cancer therapy. Finally, the DNA photocleavage of Ru-CDs was verified through the experiment of gel electrophoresis. The results suggested that the plasmid DNA could only be damaged in the presence of Ru-CDs and light. Thus, the as-prepared Ru-CDs showed good prospects and a wide range of biological applications.