MnO₂Nanospheres Assisted by Cysteine Combined with MnO₂Nanosheets as a Fluorescence Resonance Energy Transfer System for “Switch-on” Detection of Glutathione

Manganese dioxide nanosheets combined with cysteine-assisted emitting manganese dioxide nanospheres (Cys-MnO₂nanospheres) is fabricated for the first time as an “off-on” fluorescence detection platform for glutathione (GSH). In this sensing system, Cys-MnO₂nanospheres served as energy donors, while MnO₂nanosheets were used as both energy acceptors and recognition units. MnO₂nanosheets can effectively quench the fluorescence of Cys-MnO₂nanospheres through the fluorescence resonance energy transfer (FRET). The addition of GSH could reduce MnO₂nanosheets into Mn²⁺, disrupting the FRET process and restoring the fluorescence of Cys-MnO₂nanospheres. Under the optimum conditions, the “switch-on” platform we established has a wide response to GSH with a range of 5-50 μM and 150-800 μM, as well as a superior specificity. Importantly, all components of the sensor are nontoxic, biocompatible, easily prepared, and have a high utilization of raw materials. Moreover, the sensing system achieved satisfactory results in human serum, showing a tremendous potential in the field of biomedicine.