Cu2+-Modified Metal-Organic Framework Nanoparticles: A Peroxidase-Mimicking Nanoenzyme

The synthesis and characterization of UiO-type metal-organic framework nanoparticles (NMOFs) composed of Zr4+ ions bridged by 2,2'-bipyridine-5,5'-dicarboxylic acid ligands and the postmodification of the NMOFs with Cu2+ ions are described. The resulting Cu2+-modified NMOFs, Cu2+-NMOFs, exhibit peroxidase-like catalytic activities reflected by the catalyzed oxidation of Amplex-Red to the fluorescent Resorufin by H2O2, the catalyzed oxidation of dopamine to aminochrome by H2O2, and the catalyzed generation of chemiluminescence in the presence of luminol/H2O2. Also, the Cu2+-NMOFs mimic NADH peroxidase functions and catalyze the oxidation of dihydronicotinamide adenine dinucleotide, NADH, to nicotinamide adenine dinucleotide, NAD(+), in the presence of H2O2. The Cu2+-NMOFs-catalyzed generation of chemiluminescence in the presence of luminol/H2O2 is used to develop a glucose sensor by monitoring the H2O2 formed by the aerobic oxidation of glucose to gluconic acid in the presence of glucose oxidase. Furthermore, loading the Cu2+-NMOFs with fluorescein and activating the catalyzed generation of chemiluminescence in the presence of luminol/H2O2 yield an efficient chemiluminescence resonance energy transfer (CRET) process to the fluorescein reflected by the activation of the fluorescence of the dye (lambda = 520 nm, CRET efficiency 35%).