Carbon-Dot-Based Ratiometric Fluorescent Probe for Imaging and Biosensing of Superoxide Anion in Live Cells

In this article, a ratiometric fluorescent biosensor for O-2(center dot-). was developed, by employing carbon dots (C-Dots) as the reference fluorophore and hydroethidine (HE), a specific organic molecule toward O-2(center dot-), playing the role as both specific recognition element and response signal. The hybrid fluorescent probe CD-HE only emitted at 525 nm is ascribed to C-Dots, while HE was almost nonfluorescent, upon excitation at 488 nm. However, after reaction with O-2(center dot-), a new emission peak ascribed to the reaction products of HE and O-2(center dot-). was clearly observed at 610 nm. Meanwhile, this peak gradually increased with the increasing concentration of O-2(center dot-) the emission peak at 525 nm stayed constant, leading to a ratiometric detection of O-2(center dot-). The inorganic organic fluorescent sensor exhibited high sensitivity, a broad dynamic linear range of similar to 5 x 10(-7)-1.4 x 10(-4) M, and low detection limit down to 100 nM. The present probe also showed high accuracy and excellent selectivity for O-2(center dot-) over other reactive oxygen species (ROS), metal ions, and so on. Moreover, the C-Dot-based inorganic organic probe demonstrated long-term stability against pH changes and continuous light illumination, good cell-permeability, and low cytotoxicity. Accordingly, the developed fluorescent biosensor was eventually applied for intracellular bioimaging and biosensing of O-2(center dot-) changes upon oxidative stress.