Electron Transfer from Graphene Quantum Dots to the Copper Complex Enhances Its Nuclease Activity

Abstract

We previously reported that graphene oxide could enhance nuclease activity of copper complex containing aromatic ligands, thus exhibit the potential for applications in anticancer therapy. However, the functional mechanism of graphene oxide is not well understood. In this work, using graphene quantum dots (GQDs), which have smaller lateral size, better biocompatibility, and a conjugate state higher than that of graphene oxide, we investigated systematically the mechanism of GQDs in enhancing nuclease activity of copper complexes. Through a variety of spectroscopic methods, we found that GQDs promote the reduction of copper ions and accelerate their reaction with O2, forming superoxide anions and copper-centered radicals. These active species then oxidize DNA molecules. The improvement in the reduction of copper complexes can be attributed to the coordination of the GQDs to the copper center of the complex, leading to an efficient electron-transfer from the electron-rich GQDs to the copper complexes. The fundamental understanding of the role of the GQDs in DNA cleavage by the transition complexes is promising for the discovery of anticancer therapeutics. More importantly, unique and rich three-dimensional structures of metal complexes also make it possible to prepare highly active DNA cleavage reagents with a high selectivity for DNA sequences and structures.

Highly Efficient Cofactors of Cu2+‐Dependent Deoxyribozymes

“…It's still not clear why some radical scavengers are not effective. These inhibition results suggested that hydroxyl radicals might be involved during the reactions, similar to the observations when using the Cu 2+ cofactor . The result is further supported by the enhancement of the reaction rate constants in the presence of H 2 O 2 and ascorbate (Figures S7 and S8).…”

Glowing Graphene Quantum Dots and Carbon Dots: Properties, Syntheses, and Biological Applications

“…They attributed the high efficiency to the ability of GQDs to intercalate with DNA. Zheng et al carried out further systematic investigations on this cleavage mechanism . They proposed that electron rich GQDs transfer electrons to the metal complex of Cu 2+ , which in turn produces reactive oxygen species upon reduction.…”

Photoinduced and Self‐Activated Nuclease Activity of Copper(II) Complexes with N‐(Quinolin‐8‐yl)quin­olin‐8‐sulfonamide – DNA and Bovine Serum Albumin Binding

“…Recently, diverse strategies have been developed to obtain Cu II complexes that can induce DNA photocleavage. A series of Cu II polypyridyl compounds have been designed with DNA photocleavage activity,17–21 and ternary Cu II complexes with DNA‐binder phenanthroline bases and a photoactive ligand have also been prepared to enhance DNA binding and promote DNA cleavage activity 16,22…”