Novel Fluorescent Nanoprobe Based on Gold Nanoparticles and Carbon Quantum Dots for Probing and Imaging of Intracellular Glutathione

Glutathione (GSH), a tripeptide and essential antioxidant, plays a pivotal role in cellular defense by detoxifying reactive oxygen species, enhancing antioxidant activity, and maintaining redox homeostasis. Accurate measurement of GSH levels is vital for understanding health status and early disease detection. This study reports the synthesis and characterization of a novel static quenching-based fluorescent probe for GSH detection, employing sulfhydryl-functionalized Cu-doped carbon quantum dots (S-Cu@CQDs) conjugated with gold nanoparticles (GNPs). The probe demonstrates high selectivity, sensitivity, low toxicity, and stability, alongside imaging capabilities for cellular GSH. The sensing mechanism relies on static quenching of S-Cu@CQD fluorescence by GNPs, with fluorescence recovery upon GSH-induced displacement. The probe exhibits a robust linear response to GSH concentrations between 3.0 and 20.0 mM, a limit of detection of 1.0 mM, and successful imaging of GSH in MCF-7 breast cancer cells. These findings position the S-Cu@CQD/GNP conjugate as a promising tool for biomedical applications, including oxidative stress monitoring and cancer diagnostics.