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 H₂ O₂ , the catalyzed oxidation of dopamine to aminochrome by H₂ O₂ , and the catalyzed generation of chemiluminescence in the presence of luminol/H₂ O₂ . 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 H₂ O₂ . The Cu²⁺ -NMOFs-catalyzed generation of chemiluminescence in the presence of luminol/H₂ O₂ is used to develop a glucose sensor by monitoring the H₂ O₂ 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/H₂ O₂ yield an efficient chemiluminescence resonance energy transfer (CRET) process to the fluorescein reflected by the activation of the fluorescence of the dye (λ = 520 nm, CRET efficiency 35%).