MRI/Fluorescence bimodal amplification system for cellular GSH detection and tumor cell imaging based on manganese dioxide nanosheet

Here, we report a novel magnetic resonance imaging (MRI)/fluorescence bimodal amplification platform for the detection of glutathione (GSH) on the basis of redoxable manganese dioxide (MnO₂) nanosheets, which can be readily applied as a DNA nanocarrier, fluorescence quencher, and intracellular GSH-activated MRI contrast agent. The binding of aptamers that absorbed on the MnO₂ nanosheets to their target can facilitating the endocytosis of target-nanoprobes. Once endocytosed, the MnO₂ nanosheets can react with cellular GSH, resulting in the disintegration of nanosheets to generate plenty of Mn²⁺ ions for MRI and releases the primers which were adsorbed on the MnO₂ nanosheets. Then the rolling circle amplification (RCA) reaction was initiated to amplify the fluorescence signal. In addition, after treatment with GSH, the MnO₂ nanosheets were reduced and then most of the fluorescence was recovered. Therefore, this MnO₂ nanoprobe exhibits excellent selectivity, suggesting a potential detection platform for analyzing the glutathione level in cells.