Highly sensitive glutathione assay and intracellular imaging with functionalized semiconductor quantum dots

Abstract

Glutathione (GSH) plays a vital role in biological systems and is associated with human pathology. The engineering of semiconductor quantum dots (QDs) as fluorescent probes for GSH sensing and bioimaging is a potential yet rarely reported approach. Herein, we report the in situ growth of manganese dioxide nanosheets (MnO₂) on silica-coated semiconductor quantum dots (QD@SiO₂), to prepare a stable and biocompatible fluorescent nanoprobe (QD@SiO₂-MnO₂) for the selective and sensitive detection of GSH. The modification of QD@SiO₂ with MnO₂ significantly quenched the fluorescence of CdSe/ZnS QDs, yet the addition of GSH efficiently recovered the fluorescence of the nanoprobe due to the decomposition of MnO₂ by GSH. This nanosensor showed a rapid response to GSH with a low detection limit, and high selectivity towards GSH over potential interferences. Furthermore, the MnO₂-engineered QDs had good biocompatibility and cellular uptake ability, and were successfully applied for the real-time imaging of intracellular GSH. We envision that semiconductor QD-based probes will stimulate the study of GSH dynamics and facilitate the understanding of GSH-related pathophysiological events.