Carbon quantum Dot@Silver nanocomposite-based fluorescent imaging of intracellular superoxide anion

摘要

Silver nanoparticle (Ag NP)-coated carbon quantum dot (CQD) core-shell-structured nanocomposites (CQD@Ag NCs) were developed for fluorescent imaging of intracellular superoxide anion (O-2(center dot-)). The morphology of CQD@Ag NCs was investigated by transmission electron microscopy, and the composition was characterized by X-ray diffraction and X-ray photoelectron spectroscopy. CQDs display blue fluorescence with excitation/emission maxima at 360/440 nm, and the fluorescence was quenched by Ag NPs in CQD@Ag NCs. In the presence of O-2(center dot-), Ag NPs were oxide-etched and the fluorescence of CQDs was recovered. A linearity between the relative fluorescence intensity and O-2(center dot-) solution concentration within the range 0.6 to 1.6 mu M was found, with a detection limit of 0.3 mu M. Due to their high sensitivity, selectivity, and low cytotoxicity, the as-synthesized CQD@Ag NCs have been successfully applied for imaging of O-2(center dot-) in MCF-7 cells during the whole process of autophagy induced by serum starvation. In our perception, the developed method provides a cost-effective, sensitive, and selective tool in bioimaging and monitoring of intracellular O-2(center dot-) changes, and is promising for potential biological applications.