Abstract
To date, only a few reports about studies on toxic effects of carbon nanotubes (CNT) are available, and their results are often controversial. Three different cell lines (rainbow trout liver cells (RTL-W1), human adrenocortical carcinoma cells (T47Dluc), and human adrenocarcinoma cells (H295R)) were exposed to multiwalled carbon nanotubes, the antimicrobial agent triclocarban (TCC) as well as the mixture of both substances in a concentration range of 3.13 to 50 mg CNT/L, 31.25 to 500 μg TCC/L, and 3.13 to 50 mg CNT/L + 1% TCC (percentage relative to carbon nanotubes concentration), respectively. Triclocarban is a high-production volume chemical that is widely used as an antimicrobial compound and is known for its toxicity, hydrophobicity, endocrine disruption, bioaccumulation potential, and environmental persistence. Carbon nanotubes are known to interact with hydrophobic organic compounds. Therefore, triclocarban was selected as a model substance to examine mixture toxicity in this study. The influence of multiwalled carbon nanotubes and triclocarban on various toxicological endpoints was specified: neither cytotoxicity nor endocrine disruption could be observed after exposure of the three cell lines to carbon nanotubes, but the nanomaterial caused intracellular generation of reactive oxygen species in all cell types. For TCC on the other hand, cell vitality of 80% could be observed at a concentration of 2.1 mg/L for treated RTL-W1 cells. A decrease of luciferase activity in the ER Calux assay at a triclocarban concentration of 125 μg/L and higher was observed. This effect was less pronounced when multiwalled carbon nanotubes were present in the medium. Taken together, these results demonstrate that multiwalled carbon nanotubes induce the production of reactive oxygen species in RTL-W1, T47Dluc, and H295R cells, reveal no cytotoxicity, and reduce the bioavailability and toxicity of the biocide triclocarban.
Highlights
The annual worldwide production of carbon nanotubes (CNT) surpassed the multimetric ton level and is expected to further increase [1]
As many studies already showed that CNT are toxic for different cell lines [5,9], we investigated cells by determination of cytotoxicity in the neutral red retention (NR) assay and the 3-(4,5-dimethylthiazol-2-yl)2,5-diphenyl tetrazolium bromide (MTT) assay [68] to verify whether Multiwalled carbon nanotubes (MWCNT) showed a toxic potential for the used cells, namely RTL-W1, T47Dluc, and H295R
Cytotoxicity Neutral red retention assay An NR80 value of 2.1 mg/L was obtained for the biocide TCC (Figure 2)
Summary
The annual worldwide production of carbon nanotubes (CNT) surpassed the multimetric ton level and is expected to further increase [1]. Their structure gives them exceptional properties, which makes this material suitable for the use in composite materials, sensors, drug delivery, hydrogen storage fuel cells, and various environmental applications [2,3,4]. This complicates clear determination of pure MWCNT toxicity Despite these concerns, very few studies have been simultaneously conducted with various human cell lines to assess the health effects of different CNT. There is no global agreement about the risk of CNT on human health [15]
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