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 (MnO 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 MnO NS. The suppression was relieved and the two emission peaks recovered proportionally when MnO 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@MnO 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 Schematic representation of glutathione (GSH) ratiometric detection. The nanoprobe is prepared from dual-emission carbon dots (de-CDs) and manganese dioxide nanosheets (MnO NS). GSH removes quenching effect by decomposing MnO NS and induces intrinsic response of de-CDs, which realizes ratiometric detection.