In-situ formation of MnO2 nanoparticles on Ru@SiO2 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 SiO2 nanoparticles encapsulated with Ru(bpy)32+ (Ru@SiO2) were designed and synthesized as fluorescent probe to construct a GSH-switched fluorescent assay. The encapsulation of Ru(bpy)32+ in the SiO2 nanoparticles could effectively prevent the leakage of Ru(bpy)32+ molecules, improving the photostability of probe. The fluorescence of Ru@SiO2 nanoparticles was quenched by coating MnO2 nanoparticles on Ru@SiO2 surface (Ru@SiO2@MnO2 nano -composites) through an in situ growth approach, which reduced background of the assay. The MnO2 nano -particles not only further inhibited the leakage of Ru(bpy)32+ molecules, but also could serve as a recognition unit of GSH. In the presence of GSH, the MnO2 nanoparticles on the surface of Ru@SiO2 nanoparticles were reduced to Mn2+, resulting the fluorescence recovery of Ru@SiO2 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 MnO2 nanoparticles and special role of Ru@SiO2 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.