Pulmonary Biocompatibility Assessment of Inhaled Single-wall and Multiwall Carbon Nanotubes in BALB/c Mice

Abstract

With the widespread application of carbon nanotubes (CNTs) in diverse commercial processes, scientists are now concerned about the potential health risk of occupational exposures. In this study, CNT-induced pulmonary toxicity was investigated by exposing BALB/c mice to aerosolized single-wall (SW) CNT and multiwall (MW) CNT (5 g/g of mice) for 7 consecutive days in a nose-only exposure system. Microscopic studies showed that inhaled CNTs were homogeneously distributed in the mouse lung. The total number of bronchoalveolar lavage polymorphonuclear leukocytes recovered from the mice exposed to SWCNT and MWCNT (1.2 ؋ 10 6 ؎ 0.52 and 9.87 ؋ 10 5 ؎ 1.45; respectively) was significantly greater than control mice (5.46 ؋ 10 5 ؎ 0.78). Rapid development of pulmonary fibrosis in mice that inhaled CNT was also confirmed by significant increases in the collagen level. The lactate dehydrogenase levels were increased nearly 2-and 2.4-fold in mice that inhaled SWCNT and MWCNT, respectively, as compared with control mice. In addition, exposure of CNTs to mice showed a significant (p < 0.05) reduction of antioxidants (glutathione, superoxide dismutase, and catalase) and induction of oxidants (myloperoxidase, oxidative stress, and lipid peroxidation) compared with control. Apoptosis-related proteins such as caspase-3 and -8 activities were also significantly increased in mice that inhaled CNT than in control mice. Together, this study shows that inhaled CNTs induce inflammation, fibrosis, alteration of oxidant and antioxidant levels, and induction of apoptosis-related proteins in the lung tissues to trigger cell death.

MWCNTs of different physicochemical properties cause similar inflammatory responses, but differences in transcriptional and histological markers of fibrosis in mouse lungs

“…Comparing these studies to the result of the present study, we hypothesize that up-regulation of fibrosis related gene expression observed following CNT Large exposure only, could be due to the structural differences between CNT Large and CNT Small . However, it should be noted that some studies observe no differences in the fibrotic potential between CNTs of different lengths (Muller et al, 2005;Ravichandran et al, 2011).…”

Anti-Cancer Cytotoxic Effects of Multiwalled Carbon Nanotubes

“…In particular, MWCNTs promote the death of human epithelial cells [42,52,54,76,72], human lymphocytes [43,51], human macrophages [44], human connective tissues [75], human cancer cell lines [89][90][91][92], as well as many animal cell lines. Interestingly, there is also literature claiming the contrary [94][95][96][97][98][99]. This controversy illustrates the huge variability of existing CNTs in terms of lengths, diameters, surface functionalization, contaminants, etc., as well as the diverse nature of the cells used for the different in vitro toxicological assays performed.…”

Multiwall Carbon Nanotube-Induced Apoptosis and Antioxidant Gene Expression in the Gills, Liver, and Intestine ofOryzias latipes

“…Nevertheless, MWCNTs are potentially very harmful environmental pollutants because of three major factors: the shape of the particles; their surface reactivity; and their clearance difficulty [9]. To improve the mechanical properties of MWCNTs, sufficient wetting and uniform dispersion in various media, including aqueous solutions, are required [6, 10].…”