Abstract
Given the increasing use of carbon nanotubes (CNT) in composite materials and their possible expansion to new areas such as nanomedicine which will both lead to higher human exposure, a better understanding of their potential to cause adverse effects on human health is needed. Like other nanomaterials, the biological reactivity and toxicity of CNT were shown to depend on various physicochemical characteristics, and length has been suggested to play a critical role. We therefore designed a comprehensive study that aimed at comparing the effects on murine macrophages of two samples of multi-walled CNT (MWCNT) specifically synthesized following a similar production process (aerosol-assisted CVD), and used a soft ultrasonic treatment in water to modify the length of one of them. We showed that modification of the length of MWCNT leads, unavoidably, to accompanying structural (i.e. defects) and chemical (i.e. oxidation) modifications that affect both surface and residual catalyst iron nanoparticle content of CNT. The biological response of murine macrophages to the two different MWCNT samples was evaluated in terms of cell viability, pro-inflammatory cytokines secretion and oxidative stress. We showed that structural defects and oxidation both induced by the length reduction process are at least as responsible as the length reduction itself for the enhanced pro-inflammatory and pro-oxidative response observed with short (oxidized) compared to long (pristine) MWCNT. In conclusion, our results stress that surface properties should be considered, alongside the length, as essential parameters in CNT-induced inflammation, especially when dealing with a safe design of CNT, for application in nanomedicine for example.
Highlights
Potential adverse effects of carbon nanotubes (CNT) on human health are of great concern, especially if we consider their increasing use in composite materials [1] and their exploration as innovative solutions for biomedical applications [1,2,3,4,5]
After preparation of the S-CNT sample by long-term ultrasonic treatment of PS-CNT, both S-CNT and long MWCNT” (L-CNT) samples were suspended in serum-free cell culture medium and the final length range distribution was measured from several Transmission electron microscopy (TEM) pictures
Mean length was measured at 4.8 μm for S-CNT and 9.5 μm for L-CNT (Figure 2a, b, and c)
Summary
Potential adverse effects of carbon nanotubes (CNT) on human health are of great concern, especially if we consider their increasing use in composite materials [1] and their exploration as innovative solutions for biomedical applications [1,2,3,4,5]. The biological reactivity and toxicity of CNT were shown to depend on numerous physicochemical characteristics including length, diameter, structural defects, surface area, tendency to agglomerate, dispersibility in solution, presence and nature of catalyst residues, as well as surface chemistry [6,7,8,9,10,11,12,13,14,15,16,17,18,19,20]. The authors reported larger diameters for longer CNT, and different contents in soluble metals between the different CNT studied were described [21,23] As mentioned before, these physicochemical differences could in turn affect the CNT biological reactivity and subsequent toxicity, and should be considered alongside the variation in length to assess the toxicological profile of CNT
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