Versatile metal-doped carbon-based quantum dots toward biomedical diagnostic, therapeutic, and theranostic applications

Metal-doped carbon-based quantum dots (M-CQDs) have recently gained prominence as versatile theranostic nanomaterials, offering highly integrated platforms for precise diagnostics and effective therapeutics. Compared to undoped or non-metal-doped counterparts, the introduction of metal dopants, with their larger atomic radii, greater number of electrons, and available unoccupied orbitals, substantially enhances the optical, electronic, and magnetic properties of the constructed M-CQDs. This review systematically summarizes recent advances in the rational design of M-CQDs, focusing on how metal doping tailors their properties and enables diverse biomedical applications in diagnostics, therapeutics, and theranostics. Firstly, we discuss how these engineered properties enable advanced diagnostic applications, including high-resolution bioimaging and sensitive biosensing. Secondly, we detail their utilization in potent therapeutic modalities such as photothermal therapy, catalytic therapy, and chemotherapy. Furthermore, a key focus is placed on the design of multifunctional M-CQD-based nanoplatforms that seamlessly integrate diagnostic and therapeutic capabilities within a single entity for targeted and personalized medicine. Finally, we address existing challenges and future opportunities, aiming to inspire further innovation and accelerate the clinical translation of M-CQDs toward precision nanomedicine.