A nanoprobe for ratiometric imaging of glutathione in living cells based on the use of a nanocomposite prepared from dual-emission carbon dots and manganese dioxide nanosheets

A ratiometric fluorescence assay for glutathione (GSH) was developed. The novel assay is based on a nanoprobe composed of manganese dioxide nanosheets (MnO₂ NS) and dual-emission carbon dots (de-CDs) with intrinsic GSH-response property. After construction of the nanoprobe, two emission peaks of de-CDs were suppressed to varying degrees by MnO₂ NS. The suppression was relieved and the two emission peaks recovered proportionally when MnO₂ NS was decomposed by GSH, thus realizing the ratiometric assay for micromolar GSH. The intrinsic responsiveness of de-CDs to millimolar GSH broadens the analytical range of the nanoprobe. An appropriate precursor, calcon-carboxylic acid, was screened out to synthesize de-CDs via one-step hydrothermal treatment. The de-CD@MnO₂ NS nanoprobe can measure GSH concentrations through the fluorescence intensity ratio between 435 and 516 nm excited at 365 nm. The range of response was from 1 μM to 10 mM and the detection limit reached 0.6 μM (3σ criterion). Benefiting from its good biocompatibility, the proposed nanoprobe has excellent applicability for intracellular GSH imaging.Graphical abstract