In-situ formation of MnO nanoparticles on Ru@SiO nanospheres as a fluorescent probe for sensitive and rapid detection of glutathione.

Glutathione (GSH)-switched fluorescent assays have appealed much attention due to rapid signal changes of fluorescent probes. However, exposure to exterior environment of fluorescent probe causes photobleaching and premature leakage, leading to low sensitivity and poor photostability. Herein, luminescent SiO nanoparticles encapsulated with Ru(bpy) (Ru@SiO) were designed and synthesized as fluorescent probe to construct a GSH-switched fluorescent assay. The encapsulation of Ru(bpy) in the SiO nanoparticles could effectively prevent the leakage of Ru(bpy) molecules, improving the photostability of probe. The fluorescence of Ru@SiO nanoparticles was quenched by coating MnO nanoparticles on Ru@SiO surface (Ru@SiO@MnO nanocomposites) through an in situ growth approach, which reduced background of the assay. The MnO nanoparticles not only further inhibited the leakage of Ru(bpy) molecules, but also could serve as a recognition unit of GSH. In the presence of GSH, the MnO nanoparticles on the surface of Ru@SiO nanoparticles were reduced to Mn, resulting the fluorescence recovery of Ru@SiO nanoparticles. Thus, a signal-on fluorescent strategy was constructed for GSH detection. The assay displayed good analytical performance for GSH detection with a low detection limit of 16.2 nM due to excellent fluorescence quenching ability of MnO nanoparticles and special role of Ru@SiO nanoparticles to block probe leakage. The proposed assay was also applied to measure GSH levels in human serum samples. This work paves a new way to detect GSH with high sensitivity.