Red emitting carbon dots for detection of endogenous glutathione with fluorescence enhancement and cell imaging

Glutathione (GSH) as a key endogenous antioxidant plays the essential role in many bioprocesses, and the lack of GSH would result in a series of diseases. In order to develop a fluorescent indicator for monitoring the fluctuation of GSH and provide information for clinical diagnosis, the red fluorescence carbon dots containing double bonds (DB-CDs) were developed by one-pot hydrothermal process. Owing to photoinduced electron transfer (PET) process between the surface amine groups and the carbon core, the DB-CDs presented the weak fluorescence. Upon addition of GSH, PET process was inhibited by addition reaction between sulfhydryl group of GSH and double bonds, and the bright red fluorescence was exhibited with an emission maximum (λ^fl_max) of 630 nm. A good linear relationship was exhibited in the range of 0.12-75 μM with the detection limit as low as 34.6 nM. Moreover, the cell imaging and the fast kinetic data all demonstrated that the DB-CDs could detect the endogenous GSH without interferences from metal ions and other amino acids, suggesting that the DB-CDs could be used as fluorescence probe for GSH detection in living systems.