Cu-functionalized carbon nitride nanoparticles (Cu-g-CN NPs), ∼200 nm, and Cu-carbon dots (Cu-C-dots), ∼8 nm, act as horseradish peroxidase-mimicking catalysts. The nanoparticles catalyze the generation of chemiluminescence in the presence of luminol/HO and catalyze the oxidation of dopamine by HO to form aminochrome. The Cu-g-CN-driven generation of chemiluminescence is used to develop a HO sensor and is implemented to develop a glucose detection platform and a sensor for probing glucose oxidase. Also, the Cu-C-dots are functionalized with the β-cyclodextrin (β-CD) receptor units. The concentration of dopamine, at the Cu-C-dots' surface, by means of the β-CD receptor sites, leads to a 4-fold enhancement in the oxidation of dopamine by HO to yield aminochrome compared to that of the unmodified C-dots.
Zeolitic Zn-imidazolate cross-linked framework nanoparticles, ZIF-8 NMOFs, are used as "smart" glucose-responsive carriers for the controlled release of drugs. The ZIF-8 NMOFs are loaded with the respective drug and glucose oxidase (GOx), and the GOx-mediated aerobic oxidation of glucose yields gluconic acid and HO. The acidification of the NMOFs' microenvironment leads to the degradation of the nanoparticles and the release of the loaded drugs. In one sense-and-treat system, GOx and insulin are loaded in the NMOFs. In the presence of glucose, the nanoparticles are unlocked, resulting in the release of insulin. The release of insulin is controlled by the concentration of glucose. In the second sense-and-treat system, the NMOFs are loaded with the antivascular endothelial growth factor aptamer (VEGF aptamer) and GOx. In the presence of glucose, the ZIF-8 NMOFs are degraded, leading to the release of the VEGF aptamer, which acts as a potential inhibitor of the angiogenetic regeneration of blood vessels by VEGF. As calcination of the VEGF-generated blood vessels leads to blindness of diabetic patients, the functional NMOFs might act as "smart" materials for the treatment of macular diseases. The potential cytotoxicity of the NMOFs originated from the GOx-generated HO is resolved by the co-immobilization of the HO-scavanger catalase in the NMOFs.
Cu-ion-modified graphene oxide nanoparticles, Cu-GO NPs, act as a heterogeneous catalyst mimicking functions of horseradish peroxidase, HRP, and of NADH peroxidase. The Cu-GO NPs catalyze the oxidation of dopamine to aminochrome by HO and catalyze the generation of chemiluminescence in the presence of luminol and HO. The Cu-GO NPs provide an active material for the chemiluminescence detection of HO and allow the probing of the activity of HO-generating oxidases and the detection of their substrates. This is exemplified with detecting glucose by the aerobic oxidation of glucose by glucose oxidase and the Cu-GO NP-stimulated chemiluminescence intensity generated by the HO product. Similarly, the Cu-GO NPs catalyze the HO oxidation of NADH to the biologically active NAD cofactor. This catalytic system allows its conjugation to biocatalytic transformations involving NAD-dependent enzyme, as exemplified for the alcohol dehydrogenase-catalyzed oxidation of benzyl alcohol to benzoic acid through the Cu-GO NPs-catalyzed regeneration of NAD.
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