Myeloperoxidase-induced biodegradation of single-walled carbon nanotubes is mediated by hypochlorite

Abstract

Broad prospects for the use of single-walled carbon nanotubes (SWNTs) in medicine and biotechnology raise the concerns about both their toxicity, and the mechanisms of biodegradation and excretion from the body. SWNTs biodegradation as a result of catalytic activity of myeloperoxidase (MPO) was shown in the isolated MPO system as well as in the suspension of neutrophils [Kagan V.E., et al., 2010]. In the present study we analyzed the ability of different MPO-produced oxidants to participate in the modification and degradation of SWNTs. The comparison of the ability of various peroxidases to degrade SWNTs in vitro revealed that myeloperoxidase, due to its ability to produce hypochlorite, and lactoperoxidase, due to its ability to produce hypobromite, are extremely efficient in the degradation of carbon nanotubes. The biodegradation of SWNTs in the model system can also be caused by free radicals generated as a result of heme degradation and, to a lesser extent, by active oxoferryl intermediates of peroxidases. Our experiments showed that in the presence of blood plasma, peroxidase intermediates or free radical products of heme degradation were unable to initiate biodegradation of carbon nanotubes, only the generation of hypochlorite by MPO can cause the biodegradation of carbon nanotubes in vivo. Titration of SWNTs suspension containing plasma with hypochlorite at high concentrations resulted in the decrease in the optical absorbance of the suspension indicating the degradation of nanotubes. Our results clearly indicate that hypochlorite can serve as a main oxidizing agent which is able to modify and degrade nanotubes in the sites of inflammation and in the phagosomes.

Hypochlorite degrades 2D graphene oxide sheets faster than 1D oxidised carbon nanotubes and nanohorns

“…Previous studies have demonstrated the effect of ClO − on carbon nanotubes. [27][28][29][30] The authors utilised the action of myeloperoxidase to convert H 2 O 2 to ClO − , which subsequently acted to oxidise the carbon nanotubes and ultimately degrade them. The oxidative action of ClO − was confirmed, as aqueous NaClO was used as a positive control to degrade the CNMs.…”

Carbon Nanotubes as an Effective Opportunity for Cancer Diagnosis and Treatment

“…In fact, they demonstrated how functionalized SWCNTs carrying defect sites on the sidewall and tips of the carbon nanotubes could be degraded by plant-derived horse radish peroxidase (HRP) [34]. CNTs are found to be biodegradable also by means of other kind of peroxidases [35,36,37], by bacteria [38] or by other biological mechanisms [39,40]. …”

Nanoparticles, Lung Injury, and the Role of Oxidant Stress

“…Other carbon-based nanoparticles have been shown to undergo similar MPO-catalyzed modifications and degradation (16, 127). It has been proposed that hypochlorite and MPO reactive intermediates are possible pathways in which the oxidative biodegradation process occurs (15, 16, 127, 128). Certainly the biodegradation of SWCNTs has tremendous implications for biopersistence and potential long-term health effects from prolonged exposures.…”