study of a novel, safe, rapid, and targeted red carbon dot probe for recognition of tumors with high expression of folate enzyme.

Carbon dots (CDS) have been proved to be a type of ideal biological imaging probe. They have the advantages of spontaneous fluorescence, anti-photobleaching, good biocompatibility and easy surface decoration, and are receiving special attention from researchers. The early imaging diagnosis of tumors has always been a practical means of clinical diagnosis. Finding an efficient and low-toxicity tumor probe is the continuous goal of tumor clinical diagnosis and treatment. Therefore, this article uses the modifiable properties of the surface structure of carbon dots, and at the same time, uses the characteristics of tumors with high expression of folate receptors (FR) that can specifically take up folic acid (FA) to construct folic acid carbon dot conjugates (FA-CDs) to achieve targeted tumor uptake. Firstly, CCK8 toxicity tests proved that FA-DCCDs had good biocompatibility and were almost non-toxic. Further, confocal cell imaging experiments, microplate quantitative experiments and flow cytometry experiments proved that FA-CDs were selective and more easily absorbed by tumor cells with high expression of folate receptors, and bare carbon dots could be absorbed into cells without selectivity. Through experiments, the law of injection of bare CDs into the body was explored, which proved that they had no obvious accumulation and had high distribution in the liver and kidneys. FA-CDs was applied to the targeted imaging of a mouse tumor model for the first time, which proved again that the carbon point coupled with folic acid had selectivity for tumor cells with high expression of FR receptors, which provided a basis for tumor drug research and early clinical diagnosis of tumors.