A sensitive and selective chemosensor for GSSG detection based on the recovered fluorescence of NDPA-Fe3O4@SiO2-Cu(II) nanomaterial

A sensitive and selective sensor for oxidized glutathione (GSSG) detection based on the recovered fluorescence of naphthalimide-DPA (NDPA)-Fe3O4@SiO2-Cu(II) system is reported. NDPA-Fe3O4@SiO2 was characterized by X-ray power diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectra (FT-IR) and fluorophotometry. The fluorescence of NDPA-Fe3O4@SiO2 could be quenched by Cu2+ due to the coordination of Cu2+ with the tridentate receptor DPA. This coordination process reduced the electron-donating ability of the nitrogen atom in the DPA moiety, thus suppressing the internal charge transfer (ICT) process in NDPA-Fe3O4@SiO2. In the presence of GSSG, the fluorescence of NDPA-Fe3O4@SiO2-Cu(II) was recovered because of strong coordination of Cu2+ with GSSG, which promoted the decomplexation between NDPA-Fe3O4@SiO2 and Cu2+, and enhanced the ICT process. The NDPA-Fe3O4@SiO2-Cu(II) nanomaterial exhibited high sensitivity towards GSSG, and a good linear relationship was obtained from 5 nM to 60 μM. The limit of detection, based on a signal-to-noise ratio of 3, was 50 pM. In addition, the presence of magnetic Fe3O4 nanoparticles (NPs) in NDPA-Fe3O4@SiO2 NPs would also facilitate the magnetic separation of NDPA-Fe3O4@SiO2 from the solution. Through the use of added internal standards, we successfully determined the concentration of GSSG in HEK 293 cell lysate to be 1.15 μM by the prepared chemsensor NDPA-Fe3O4@SiO2-Cu(II). The proposed method is anticipated to fabricate other sensitive fluorescence sensors based on organic-inorganic hybrid magnetic nanoparticles.