Antioxidant nanotubes: Amino acids aid radical assimilation

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  • Published: Jan 7, 2013
  • Author: David Bradley
  • Channels: Infrared Spectroscopy
thumbnail image: Antioxidant nanotubes: Amino acids aid radical assimilation

Wall to wall antioxidants

Multi-walled carbon nanotubes functionalized by sonication with various amino acids can act as synthetic antioxidants. IR spectroscopy and other techniques have been used to study their effects and reveal these entities to be more potent than other synthetic agents in scavenging free radicals.

Amino acid functionalised nanotubes scavenge free radicals faster than conventional synthetic antioxidants.

Multi-walled carbon nanotubes functionalized by sonication with various amino acids can act as synthetic antioxidants. IR spectroscopy and other techniques have been used to study their effects and reveal these entities to be more potent than other synthetic agents in scavenging free radicals.

Ahm Amiri of the Department of Engineering at the Islamic Azad University, in Marvdasht, Iran, and colleagues Mina Memarpoor-Yazdi, Mehdi Shanbedi, Hossein Eshghi, writing in the Journal of Biomedical Materials Research A explain how they are keen to develop potent antioxidants able to scavenge free radicals. Free radicals are implicated in oxidative reactions involved in diabetes mellitus, certain forms of cancer and cardiovascular disease.

Synthetic supplementation

While dietary intake or supplementation of antioxidants might seem to be the most natural approach to tackling free radicals, synthetic antioxidants have been developed that could offer a much more targeted, medicinal approach than simply increasing one's intake of vegetables in disease conditions. Compounds such as butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) have been developed for radical scavenging but pose their own health risks. The researchers suggest that carbon nanotubes, themselves antioxidants, might also be used to carry antioxidants to be directed towards specific sites in the body for therapeutic effect.

The Iranian team points out that other researchers have demonstrated that some amino acids, such as aromatic, hydrophobic, acidic, or basic amino acids can act as antioxidants. Tryptophan, tyrosine, arginine, lysine, cysteine, and histidine, for instance have antioxidant properties. Aromatic amino acids are proton donors to electron-deficient radicals and so can stabilize radicals and act as scavengers. Histidine is also a metal ion chelator and an effective free radical scavenger, the team says.

Amino roll-call

The amino acids lysine, arginine, cysteine, histidine, and aspartic acid were used to functionalise multi-walled carbon nanotubes. The team then used infrared spectroscopy, Raman spectroscopy and thermogravimetric analysis to investigate the nanotube surfaces. They found that the nanotubes were successfully functionalised and that the presence of the amino acids allowed the nanotubes to be better dispersed in aqueous solution. The team then tested the antioxidant activity of the treated nanotubes using 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), 1,1-diphenyl-2-picrylhydrazyl (DPPH), and hydroxyl radical scavenging, metal ion chelating, and reducing power assays. The products were up to twice as effective as BHA in radical scavenging and up to ten times more effective than reduced glutathione (GSH). "The results provide a considerable opportunity for developing functionalized MWCNTs as novel and effective antioxidant compounds," the team concludes. "However, more studies need to evaluate their antioxidant potential in vivo."

Related Links

J Biomed Mater Res A, 2012, online: "Influence of different amino acid groups on the free radical scavenging capability of multi walled carbon nanotubes."

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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