Reactivity of carbon nanotubes: free radical generation or scavenging activity?
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.
Dipartimento di Chimica Inorganica, Chimica Fisica e Chimica dei Materiali, Interdepartmental Center G. Scansetti for Studies on Asbestos, Italy.
Ivana
I
Fenoglio
Maura
M
Tomatis
Dominique
D
Lison
Julie
J
Muller
Antonio
A
Fonseca
Janos B
JB
Nagy
Bice
B
Fubini
D016166:Free Radical Scavengers / Q000494:pharmacology*; D005609:Free Radicals / Q000378:metabolism*; D017665:Hydroxyl Radical / Q000737:chemistry; D008168:Lung / Q000187:drug effects*; D037742:Nanotubes, Carbon / Q000737:chemistry / Q000633:toxicity*; D013481:Superoxides / Q000737:chemistry
D016166:Free Radical Scavengers; D005609:Free Radicals; D037742:Nanotubes, Carbon; D013481:Superoxides; D017665:Hydroxyl Radical