MOF-derived magnetic trimetallic oxide-carbon nanocomposites for modification-free and dual molecular events-dependent ratiometric electrochemical analysis of intracellular glutathione

The response of ratiometric electrochemical signals toward the targets of interest generally depends on specific molecules-mediated single molecular recognition event, which limits the application in analyzing the targets without specific recognition molecules. In this work, novel dual molecular recognition events were proposed for rapid and reliable electrochemical analysis of glutathione (GSH) using MOF-derived trimetallic oxide-carbon (Fe3O4/CuO/NiO-C) nanocomposites. The binding of GSH to CuO caused a decrease in the oxidation signal of Cu(Ⅱ) due to the formation of nonelectroactive complex, while NiO could electrocatalyze the oxidation of GSH. These GSH-involved dual molecular recognition events guaranteed the readout of ratiometric electrochemical signals with a complementary response range, allowing sensitive and wide-range analysis of GSH. Besides, the difference in spatial conformation gave rise to a different oxidation potential for different biothiols, which guaranteed selective analysis of GSH. The presence of Fe3O4 allowed modification-free detection within 5 min using a magnetic working electrode. Taking advantage of these merits, the developed electrochemical sensor could rapidly and reliably monitor the intracellular GSH.