Redox-responsive degradation of DNA@MnO2 nanoprobe triggering DNAzyme recycling amplification for sensitive and label-free detection of glutathione

In this work, a novel fluorescence nanoprobe based on MnO2 nanosheets and DNAzyme cyclic amplification was developed for label-free detection of GSH. In our design, the DNA@MnO2 nanoprobe was facilely prepared through the adsorption of DNA probes on the surface of MnO2 nanosheets. Importantly, MnO2 nanosheets in the DNA@MnO2 nanoprobe can act as the recognizer of analytical target GSH. In the presence of GSH, the DNA@MnO2 nanoprobe are decomposed owing to redox-responsive reaction between GSH and MnO2 nanosheets, resulting in the generation of abundant Mn2+ and the desorption of DNA probes. Subsequently, the Mn2+-dependent DNAzyme recycling amplification was rapidly initiated and a large number of the blocked G-rich sequences in DNA probes was released. The G-rich sequences were efficiently folded into G-quadruplex structures, which can remarkably light up the fluorescence intensity of thioflavin T (ThT). Experimental data demonstrated that the DNA@MnO2 nanoprobes for GSH detection have a wide linear range from 0 to 2000 µM. Moreover, this fluorescence sensing strategy was successfully applied for the detection of GSH in complex biological media with satisfying results, providing a simple, facile and cost-efficient nanoplatform for GSH-related clinical disease diagnosis.