Abstract
Carbon nanotubes (CNTs) are promising products in industry and medicine, but there are several human health concerns since their fibrous structure resembles asbestos. The presence of transition metals, mainly iron, in the fibres seems also implicated in the pathogenetic mechanisms. To unravel the role of iron at mesothelial level, we compared the chemical changes induced in MeT-5A cells by the exposure to asbestos (crocidolite) or CNTs at different content of iron impurities (raw-SWCNTs, purified- and highly purified-SWCNTs). We applied synchrotron-based X-Ray Fluorescence (XRF) microscopy and soft X-ray imaging (absorption and phase contrast images) to monitor chemical and morphological changes of the exposed cells. In parallel, we performed a ferritin assay. X-ray microscopy imaging and XRF well localize the crocidolite fibres interacting with cells, as well as the damage-related morphological changes. Differently, CNTs presence could be only partially evinced by low energy XRF through carbon distribution and sometimes iron co-localisation. Compared to controls, the cells treated with raw-SWCNTs and crocidolite fibres showed a severe alteration of iron distribution and content, with concomitant stimulation of ferritin production. Interestingly, highly purified nanotubes did not altered iron metabolism. The data provide new insights for possible CNTs effects at mesothelial/pleural level in humans.
Highlights
Nanotechnology has become one of the most promising fields in science and technology, with increasing number of applications in materials science, sensing, bioimaging, medicine and biology[1,2,3]
One of the first alarming report comes from Takagi A. et al and describes an in vivo study where the single injection of long and short MWCNTs into the peritoneal cavity of mice induced the development of mesothelioma[21]
In some carbon nanotubes (CNTs) studies bioavailable iron has been associated with increased oxidative stress[29] and inflammatory responses[30]
Summary
Nanotechnology has become one of the most promising fields in science and technology, with increasing number of applications in materials science, sensing, bioimaging, medicine and biology[1,2,3]. Since the beginning of the 21st century, the unique properties of carbon nanotubes (CNTs) made them very promising candidates in nanomedicine for biomedical applications, for drug delivery and gene therapy, and for tissue regeneration and diagnostic biosensoring[7,8,9]. Thanks to their unique surface area, excellent chemical stability, and rich electronic polyaromatic structure, they are able to absorb or conjugate with a wide variety of therapeutic molecules (drugs, proteins, antibodies, DNA, enzymes, etc.) and they have been proven to be an excellent vehicle for drug delivery by penetrating into the cells directly and keeping the drug intact without metabolism during transport through the body[10,11]. The length-dependent response to CNT demonstrated by many studies, both in vivo and in vitro, suggests that the longest fibres are those implicated in mesothelioma development as well as in inflammatory responses[19,23,24,25]
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