Abstract
BackgroundCarbon nanotubes (CNT) are a family of materials featuring a large range of length, diameter, numbers of walls and, quite often metallic impurities coming from the catalyst used for their synthesis. They exhibit unique physical properties, which have already led to an extensive development of CNT for numerous applications. Because of this development and the resulting potential increase of human exposure, an important body of literature has been published with the aim to evaluate the health impact of CNT. However, despite evidences of uptake and long-term persistence of CNT within macrophages and the central role of those cells in the CNT-induced pulmonary inflammatory response, a limited amount of data is available so far on the CNT fate inside macrophages. Therefore, the overall aim of our study was to investigate the fate of pristine single walled CNT (SWCNT) after their internalization by macrophages.MethodsTo achieve our aim, we used a broad range of techniques that aimed at getting a comprehensive characterization of the SWCNT and their catalyst residues before and after exposure of murine macrophages: X-ray diffraction (XRD), High Resolution (HR) Transmission Electron Microscopy (TEM), High Angle Annular Dark Field-Scanning TEM (HAADF-STEM) coupled to Electron Energy Loss Spectroscopy (EELS), as well as micro-X-ray fluorescence mapping (μXRF), using synchrotron radiation.ResultsWe showed 1) the rapid detachment of part of the iron nanoparticles initially attached to SWCNT which appeared as free iron nanoparticles in the cytoplasm and nucleus of CNT-exposed murine macrophages, and 2) that blockade of intracellular lysosomal acidification prevented iron nanoparticles detachment from CNT bundles and protected cells from CNT downstream toxicity.ConclusionsThe present results, while obtained with pristine SWCNT, could likely be extended to other catalyst-containing nanomaterials and surely open new ways in the interpretation and understanding of CNT toxicity.
Highlights
Carbon nanotubes (CNT) are a family of materials featuring a large range of length, diameter, numbers of walls and, quite often metallic impurities coming from the catalyst used for their synthesis
The diameter of the pristine single walled CNT (SWCNT) used in the present study has been previously evaluated by some of us [14] and estimated to be in the 0.8-1.2 nm range, while their individual length was in the 100–1000 nm range, according to supplier information
X-ray diffraction (XRD) experiments revealed intense peaks at low wave-vector Q values characteristic of SWCNT organized in bundles, while weaker peaks at higher wave-vectors corresponded to the signal of iron-based nanocrystals of cementite Fe3C (Figure 1a)
Summary
Carbon nanotubes (CNT) are a family of materials featuring a large range of length, diameter, numbers of walls and, quite often metallic impurities coming from the catalyst used for their synthesis They exhibit unique physical properties, which have already led to an extensive development of CNT for numerous applications. Carbon nanotubes (CNT) are a family of nanomaterials featuring a large range of length, diameter, numbers of walls (single-walled -SWCNT-, double-walled -DWCNTor multi-walled -MWCNT-) and, most often metallic impurities coming from the catalyst used for their synthesis. They exhibit unique physical properties, which have already led to their extensive use in composite materials [1].
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