title: The role of the iron catalyst in the toxicity of multi-walled carbon nanotubes (MWCNTs).
abstract: This study aimed to investigate the role of iron, used as a catalyst, in the biological response to pristine and functionalized multi-walled carbon nanotubes (p/fMWCNTs) with an iron content of 2.5-2.8%. Preliminarily, we assessed the pro-oxidant activity of MWCNTs-associated iron by an abiotic test. To evaluate iron bioavailability, we measured intracellular redox-active iron in A549 cells exposed to both MWCNT suspensions and to the cell medium preconditioned by MWCNTs, in order to assess the iron dissolution rate under physiological conditions. Moreover, in exposed cells, we detected ROS levels, 8-oxo-dG and mitochondrial function. The results clearly highlighted that MWCNTs- associated iron was not redox-active and that iron leakage did not occur under physiological conditions, including the oxidative burst of specialized cells. Despite this, in MWCNTs exposed cells, higher level of intracellular redox-active iron was measured in comparison to control and a significant time-dependent ROS increase was observed (P<0.01). Higher levels of 8-oxo-dG, a marker of oxidative DNA damage, and decreased mitochondrial function, confirmed the oxidative stress induced by MWCNTs. Based on the results we believe that oxidative damage could be attributable to the release of endogenous redox-active iron. This was due to the damage of acidic vacuolar compartment caused by endocytosis-mediated MWCNT internalization.
authors.affiliation: Department of Biomedical and Dental Sciences and Morphofunctional Imaging, University of Messina, Italy. Electronic address: gvisalli@unime.it.
authors.forename: Giuseppa
authors.initials: G
authors.lastname: Visalli
authors.affiliation: Department of Biomedical and Dental Sciences and Morphofunctional Imaging, University of Messina, Italy. Electronic address: alessiof1976.af@gmail.com.
authors.forename: Alessio
authors.initials: A
authors.lastname: Facciolà
authors.affiliation: Department of Electronic Engineering, Industrial Chemistry and Engineering, University of Messina, Italy. Electronic address: diannazzo@unime.it.
authors.forename: Daniela
authors.initials: D
authors.lastname: Iannazzo
authors.affiliation: Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Italy.
authors.forename: Anna
authors.initials: A
authors.lastname: Piperno
authors.affiliation: Department of Electronic Engineering, Industrial Chemistry and Engineering, University of Messina, Italy. Electronic address: apiperno@unime.it.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Pistone
authors.affiliation: Department of Biomedical and Dental Sciences and Morphofunctional Imaging, University of Messina, Italy. Electronic address: adipietr@unime.it.
authors.forename: Angela
authors.initials: A
authors.lastname: Di Pietro
mesh_terms: D000072283:A549 Cells; D056809:Alveolar Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D006801:Humans; D007501:Iron / Q000737:chemistry*; D037742:Nanotubes, Carbon / Q000009:adverse effects / Q000737:chemistry*; D018384:Oxidative Stress / Q000187:drug effects; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D037742:Nanotubes, Carbon; D017382:Reactive Oxygen Species; D007501:Iron
keywords: Acid-treated multi-walled carbon nanotubes (fMWCNT); Alveolar epithelial cell line; Iron; Oxidative damage; Pristine multi-walled carbon nanotubes (pMWCNT)