Highly efficient conversion of superoxide to oxygen using hydrophilic carbon clusters

Errol L G Samuel, Daniela C. Marcano, Vladimir Berka, Brittany R. Bitner, Gang Wu, Austin Potter, Roderic H. Fabian, Robia G. Pautler, Thomas A. Kent, Ah Lim Tsai, James M. Tour

Research output: Contribution to journalArticlepeer-review

166 Scopus citations


Many diseases are associated with oxidative stress, which occurs when the production of reactive oxygen species (ROS) overwhelms the scavenging ability of an organism. Here, we evaluated the carbon nanoparticle antioxidant properties of poly(ethylene glycolated) hydrophilic carbon clusters (PEG-HCCs) by electron paramagnetic resonance (EPR) spectroscopy, oxygen electrode, and spectrophotometric assays. These carbon nanoparticles have 1 equivalent of stable radical and showed superoxide (O2•-) dismu-tase-like properties yet were inert to nitric oxide (NO•) as well as peroxynitrite (ONOO-). Thus, PEG-HCCs can act as selective antioxidants that do not require regeneration by enzymes. Our steadystate kinetic assay using KO2 and direct freeze-trap EPR to follow its decay removed the rate-limiting substrate provision, thus enabling determination of the remarkable intrinsic turnover numbers of O2•-to O2 by PEG-HCCs at >20,000 s-1 . Themajor products of this catalytic turnover are O2 and H 2 O 2, making the PEG-HCCs a biomimetic superoxide dismutase.

Original languageEnglish (US)
Pages (from-to)2343-2348
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number8
StatePublished - Feb 24 2015


  • Antioxidant
  • Carbon nanoparticles
  • Hydrophilic carbon clusters
  • Superoxide
  • Superoxide dismutase mimetic

ASJC Scopus subject areas

  • General


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