Carbon nanotubes may protect DNA from oxidation

November 16, 2012

Scanning electron microscope image of a typical sample of the NIST single-wall carbon nanotube soot standard reference material. Recent NIST research suggests that, at least in the laboratory, carbon nanotubes may help protect DNA molecules from damage by oxidation. The image shows an area just over a micron (millionth of a meter) wide. (Color added for clarity.) (Credit: Credit: Vladar/NIST)

Single-wall carbon nanotubes (SWCNTs) may help protect DNA molecules from damage by oxidation, researchers at the National Institute of Standards and Technology (NIST) have found.

In nature, oxidation is a common chemical process in which a reactive chemical removes electrons from DNA and may increase the chance for mutations in cells.

More studies are needed to see if the in vitro protective effect of nanotubes reported in the laboratory also occurs in vivo, that is, within a living organism.

NIST researchers investigated the impact of ultrasonication on a solution of DNA fragments known as oligomers in the presence and absence of carbon nanotubes. Ultrasonication is a standard laboratory technique that uses high-frequency sound waves to mix solutions, break open cells or process slurries.

The process can break water molecules into highly reactive agents, such as hydroxyl radicals and hydrogen peroxide, that are similar to the oxidative chemicals that commonly threaten mammalian cell DNA, although the experimental levels from sonication are much greater than those found naturally within cells.

Carbon nanotubes as scavengers

Contrary to the expectation that carbon nanotubes will damage biomolecules they contact, the researchers found that overall levels of accumulated DNA damage were significantly reduced in the solutions with nanotubes present, said Elijah Petersen, one of the authors of the study.

A possible explanation for the surprising result, Petersen says, is that the carbon nanotubes may act as scavengers, binding up the oxidative species in solution and preventing them from interacting with DNA. “We also saw a decrease in DNA damage when we did ultrasonication in the presence of dimethyl sulfoxide (DMSO), a chemical compound known to be a hydroxyl radical scavenger.”

Petersen says that a third experiment where ultrasonication was performed in the presence of DMSO and SWCNTs at the same time produced an additive effect, reducing the DNA damage levels more significantly than either treatment alone.

This research is part of NIST’s work to help characterize the potential EHS risks of nanomaterials, and develop methods for identifying and measuring them.

These findings may be related to University of Paris research showing that the molecule fullerene (C60 or “buckyballs”) dissolved in olive oil fed to rats almost doubles their lifespan, possibly due to the attenuation of age-associated increases in oxidative stress (see Fullerene C60 administration doubles rat lifespan with no toxicity“).

Proposed scheme by which SWCNTs are able to scavenge ultrasonication-generated oxygen radicals and/or free electrons, leading to an overall reduction in the measured levels of oxidatively induced damage to DNA bases. The scheme illustrates the mechanism for the hydroxyl radical and electron scavenging capacity of SWCNTs in the presence of guanine and/or thymine bases. (Credit: Elijah J. Petersen et al./Small)