Fluorine–Nitrogen Codoped Carbon Dots for Visualization Imaging of Nucleic Acids via Two-Photon Fluorescence Lifetime Microscopy

Fluorescence imaging is a key tool for visualizing the morphology and dynamics of nucleic acids (DNA and RNA) in living cells to understand their role in regulating the growth, development, and reproduction of organisms. However, effective probes capable of simultaneously targeting both DNA and RNA, as well as tools for analyzing their distribution and relative ratios in organisms, are currently lacking. Therefore, fluorine-nitrogen codoped carbon dots with two-photon absorption (F-NCDs) were synthesized by the hydrothermal method and exhibited stable fluorescence, good biocompatibility, and a fluorescence lifetime sensitive to nucleic acids (DNA and RNA). The as-prepared F-NCDs act as a probe to quantify and distinguish the distribution of DNA and RNA in the nucleus via multicolor imaging by two-photon fluorescence lifetime microscopy (TP-FLIM). The method was particularly effective in tracking changes in the DNA/RNA distribution in plant cell nuclei (onion root tips) during different division stages and distinguishing animal tissues (zebrafish). The development of F-NCDs provides insights into the preparation of two-photon carbon dots and offers an effective visualization tool for TP-FLIM to dynamically study the function of genetic material in various life activities.