Fabrication of Graphitic Carbon Nitride Quantum Dots and Their Application for Simultaneous Fluorescence Imaging and pH‐Responsive Drug Release

Abstract

Abstract A simple approach is developed to produce fluorescent graphitic carbon nitride quantum dots (g‐CNQDs) by refluxing bulk graphitic carbon nitride (g‐C 3 N 4 ) in HNO 3 followed by a direct hydrothermal treatment. Owing to their small size, intrinsic optical properties, low toxicity, and useful non‐covalent interactions with the antitumor drug doxorubicin (DOX), g‐CNQDs are investigated as fluorescent nanocarriers for DOX without any pre‐modification. The inherent fluorescence of g‐CNQDs and DOX provides the drug delivery system (g‐CNQDs‐DOX) with dual‐color imaging for revealing the intracellular localization of g‐CNQDs and DOX release. The release profiles of DOX from g‐CNQDs‐DOX reveal a strong dependence on the environmental pH value, which is beneficial for mollifying side effects following chemotherapy. Cellular uptake of g‐CNQDs‐DOX indicates that not only DOX but also some g‐CNQDs penetrate cell nuclei after 16 h of incubation, which leads g‐CNQDs‐DOX to be more toxic than DOX. The results demonstrate the feasibility of using g‐CNQDs as a traceable and pH‐responsive drug delivery system due to their unique structural properties.