Fluorescence Imaging, Metabolism, and Biodistribution of Biocompatible Carbon Dots Synthesized Using Punica granatum L. Peel

In this study, a green, low-cost strategy is reported for the synthesis of carbon dots (CDs) using Punica granatum L. A systematic metabolic analysis and determination of the biodistribution of the nitrogen-doped carbon dots was conducted in vivo in mice. Fluorescence images of carbon dots in the whole body, in individual organs (kidney, gallbladder, and bladder), and in two cell lines from different tissue sources were observed. The results suggest not only that the carbon dots are fluorescent in solution, as reported previously, but also that they behave well as contrast agents in live mice. Moreover, metabolic process curves of carbon dots in blood and urine were obtained for the first time. Unlike quantum dots, which can persist in the body for more than 7 days, the carbon dots diffused and were excreted very quickly after injection into mice; within 3 min, fluorescence could be observed in blood, tissue and urine, indicating the rapid distribution of CDs. The fluorescence faded by approximately 4 h in organs and by approximately 10 h in urine, indicating that the CDs were excreted completely in half a day. Our results on the absorption, distribution, metabolism, and excretion of carbon dots may have great significance for the application of these CDs in drug delivery, as drug targets, and for biological imaging. We also demonstrated that these CDs have good biocompatibility for use in studies of mother-child barriers and in fluorescence imaging in plants.