Signal-on fluorescent sensor based on GQDs–MnO2 composite for glutathione

Abstract

Graphene quantum dots (GQDs) exhibit strong photoluminescence, biocompatibility, and low toxicity and can easily functionalize surfaces to improve the detection of biomolecules. As-prepared MnO₂ nanosheets were applied in the fabrication of GQDs–MnO₂ composite to develop a signal-on fluorescent platform for sensing glutathione (GSH). The fluorescence of the GQDs was quenched by MnO₂ in the GQDs–MnO₂ composite as a result of fluorescence resonance energy transfer within the composite. The fluorescence of GQDs was restored when GSH was introduced because GSH reduced the MnO₂ nanosheets into Mn²⁺ and released GQDs. Under the optimized conditions, the concentration of GSH can be accurately detected with high sensitivity and specificity in Tris–HCl buffer and simulated serum. The proposed sensing strategy was successfully used to measure GSH in the range of 1–1000 μM with a detection limit of 0.45 μM. In addition, GSH in reduced glutathione injection and reduced glutathione tablets can be determined accurately using the proposed method. GQDs–MnO₂ composite is thus a promising GSH fluorescence sensor for the analysis of complex systems and for quality control in the pharmaceutical industry.