Exploring multi-element co-doped carbon dots as dual-mode probes for fluorescence/CT imaging

Osteosarcoma (OS), the most common pediatric malignant bone tumor, has been stagnant in its current treatment status due to its highly heterogeneous, aggressive, and lethal nature. Herein, we developed multi-element charge-transfer co-doped carbon dots (CDs) as dual-mode contrast agents for OS models using hydrothermal carbonization. The obtained P, W co-doped CDs, P, W, Hf co-doped CDs-1, and P, W, Hf co-doped CDs-2 have high long-wavelength quantum yields (16.5, 27.3, and 14.2%) in N, N-dimethylformamide solution, which can be attributed to the presence of valence electrons in the doped metal ions or metal hydrochloride, which promotes the radiative recombination of electrons and the formation of holes. Moreover, P, W, Hf co-doped CDs-1 exhibited higher biocompatibility, good 143B cell imaging, and fluorescence/CT high contrast imaging performance in Balb/C tumor-bearing mice compared to P, W co-doped CDs, and P, W, Hf co-doped CDs-2. In addition, the biodistribution and pharmacokinetic results further indicate that P, W, Hf co-doped CDs-1 has apparent advantages in imaging tracking and biosafety of OS and has excellent potential as a dual-mode imaging contrast agent.