Reactivity of carbon nanotubes: free radical generation or scavenging activity?
ABSTRACT Carbon nanotubes (CNTs) currently attract intense research efforts because of their unique properties which make them suitable for many industrial applications. When inhaled, CNTs constitute a possible hazard to human health. Several studies have shown that when instilled in the lung of experimental animals, CNTs induced an inflammatory and fibrotic response similar to that caused by other toxic particles which might be the result of oxidative stress caused by particle- and/or cell-derived free radicals. There is, however, no direct experimental evidence of a capacity of carbon nanotubes to generate directly free radicals. Here we report that multiwall carbon nanotubes (MWCNT) in aqueous suspension do not generate oxygen or carbon-centered free radicals in the presence of H2O2 or formate, respectively, as detected with the spin-trapping technique. Conversely, we observed that, when in contact with an external source of hydroxyl or superoxide radicals, MWCNT exhibit a remarkable radical scavenging capacity. It is therefore possible that the inflammatory reaction reported in vivo must be ascribed to MWCNT features other than particle-derived free radical generation.
- Angewandte Chemie International Edition 12/2001; 40(21):4002-4005. · 13.73 Impact Factor
- American Journal of Respiratory and Critical Care Medicine 06/1998; 157(5 Pt 1):1666-80. · 11.04 Impact Factor
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ABSTRACT: The spin trapping of superoxide by nitrone spin traps, in particular 5,5-dimethyl-1-pyrroline-1-oxide (DMPO), was found to lead to the de novo production of hydroxyl radical and a nonradical species. Hydroxyl radical is then spin-trapped by DMPO, producing DMPO-OH. It was determined that a background level of approximately 3% DMPO-OH relative to DMPO-OOH is produced by this mechanism. Thus, the detection of hydroxyl radical by spin trapping with DMPO must be used with caution if the level of hydroxyl radical is less than 3% of the rate of superoxide generation. Several examples are cited in which investigators suggested that hydroxyl radical is produced when in fact the spin trapping of this free radical may have been an artifact of the system.Molecular Pharmacology 04/1982; 21(2):262-5. · 4.41 Impact Factor