Switching-Type Fluorescence Probe Based on Carbon Dot Nanocomposites for the Visual Detection of Superoxide Anions

Superoxide anion (O₂⁻), as a crucial member of reactive oxygen species (ROS), plays a pivotal role in cellular function regulation within biological systems and has been extensively implicated in the pathogenesis and progression of numerous diseases. In this paper, we successfully prepare a switching fluorescent probe (O-QD@Ag) for visual monitoring of superoxide anion (O₂⁻) by coating silver nanolayer on the surface of carbon quantum dots (CQDs). The experimental results show that the fluorescence signal of the composite is quenched in the presence of silver nanolayers. A good linear relationship between the fluorescence intensity of the probe and the O₂⁻ concentration is observed within the range of 0.2-2 µM, with a calculated detection limit (LOD) of 190 nM (LOD=[Formula: see text]). This demonstrates the probe's capability for sensitive and quantitative detection of O₂⁻ in biological systems. In addition, O-QD@Ag composite exhibits excellent biocompatibility and low toxicity, which is characterized by low toxicity in normal MCF-10 A and MDA-MB-436 cancer cells, and is suitable for selective detection of intracellular O₂⁻. To sum up, the probe not only provides an effective means to monitor the pathological process of chronic diseases such as cancer, cardiovascular diseases and neurodegenerative diseases but also shows the potential value of application in disease prognosis evaluation.