Abstract
Here, we report the synthesis of a quantum dot (QD)-DNA covalent conjugate to be used as an H2O2-free DNAzyme system with oxidase activity. Amino-coupling conjugation was carried out between amino-modified oligonucleotides (CatG4-NH2) and carboxylated quantum dots (CdTe@COOH QDs). The obtained products were characterized by spectroscopic methods (UV-Vis, fluorescence, circular dichroizm (CD), and IR) and the transmission electron microscopy (TEM) technique. A QD-DNA system with a low polydispersity and high stability in aqueous solutions was successfully obtained. The catalytic activity of the QD-DNA conjugate was examined with Amplex Red and ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate)) indicators using reactive oxygen species (ROS) generated by visible light irradiation. The synthesized QD-DNAzyme exhibited enhanced catalytic activity compared with the reference system (a mixture of QDs and DNAzyme). This proved the assumption that the covalent attachment of DNAzyme to the surface of QD resulted in a beneficial effect on its catalytic activity. The results proved that the QD-DNAzyme system can be used for generation of the signal by light irradiation. The light-induced oxidase activity of the conjugate was demonstrated, proving that the QD-DNAzyme system can be useful for the development of new cellular bioassays, e.g., for the determination of oxygen radical scavengers.
Highlights
Reactive oxygen species (ROS) are oxygen compounds that have a higher reactivity than molecular oxygen in the triplet state
We proved that the immobilization of DNA on quantum dot (QD) increases the activity of DNAzyme
The QD-DNA conjugate was successfully obtained by amino coupling, using Ethyl-3-(3-dimethylamino propyl) carbodiimide hydrochloride (EDC) and NHS as a coupling reagents
Summary
Reactive oxygen species (ROS) are oxygen compounds that have a higher reactivity than molecular oxygen in the triplet state. ROS are involved in many cellular processes These include oxidative-phosphorylation coupling that occurs in mitochondria and provides energy for cell apoptosis or programmed self-destruction of the cells [4,5,6]. QDs are semiconductor nanocrystals with sizes ranging from 1 to 10 nm. QDs can be modified, which provides a wide range of applications in medicine and diagnostics [25,26,27]. Another of their advantages is their semiconductor properties, Int. J.
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