PNNL

Abstract

Reactive oxygen species (ROS) are common cellular oxidants that, when overproduced by cellular stressors, cause harm to cells. Detection of ROS is of utmost importance to understand a wide variety of cellular function and toxicity mechanisms. Conventional ROS fluorescence assays involve using a single dye to visualize ROS quantity. Herein, we describe an ROS-sensitive fluorescent dye-incorporated carbon dot with dual fluorescence capabilities and good biocompatibility. Carbon dots (CDs) made of citric acid and urea were synthesized with incorporated cyanine-3-amine (Cy3), a bright red fluorescent dye, to create Cy3-CDs. To get Cy3 into the ROS-sensitive form, this work demonstrated that Cy3 alone and Cy3 within carbon dots can be electrochemically reduced to its colorless ROS-sensitive form. Cy3, CDs, and Cy3-CDs are all responsive to additions of superoxide, leading to an increase in fluorescence. Other oxidizers, such as hydrogen peroxide and potassium permanganate, quench CD, Cy3, and Cy3-CD fluorescence. Overall, this work examines how oxidizers interact with CDs, Cy3, and Cy3-CDs and molecular-level hypothesis are explored that will inform the design of future carbon dot-based ROS sensors.