Folic acid conjugated carbon dots doped metal-organic framework materials for cell imaging

Abstract

Folate receptor is one of the common biomarkers, which can be used for early diagnosis of cancer. Folic acid has bind specifically to folate receptor. Herein, folic acid is co-conjugated with carbon dots (FA-CDs) to achieve fluorescence imaging of tumor cells because CDs have excellent fluorescence properties, low toxicity, and good biocompatibility. In consideration of complex environment of organisms, metal-organic framework material as the host material is used for improving the stability of FA-CDs. In view of the negatively charged FA-CDs, positively charged UiO-66-NH2 was chosen as host material. Fluorescent CDs were synthesized from citric acid and urea using microwave method. And folic acid was conjugated with CDs by 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide. FA-CDs@UiO-66-NH2 composite material was obtained by adsorption method, which had a great stability and anti-interference capability under different salt concentrations, pH, and coexistence substances. And FA-CDs@UiO-66-NH2 had low toxicity in both normal cells and tumor cells. Concurrently, composite material could realize fluorescence imaging in RAW cells and COS-7 cells, manifesting FA-CDs@UiO-66-NH2 possessed the capable of fluorescence imaging.