Carbon nanomaterial toxicity

Challeng es for assessing carbon nanomaterial toxicity to the skin. Carbon, 44 (6), 1070-1078. 

While these techniques are widely used, they do not provide sufficient purity. Liquid phase purification is not an environmentally friendly process and requires corrosion-resistant equipment, as well as costly waste disposal processes. Alternative dry chemistry approaches, such as catalyst-assisted oxidation or ozone-eiuiched air oxidation, also require the use of aggressive substances or supplementary catalysts, which result in an additional contamination. Moreover, in many previous studies trial and error rather than insight and theory approaches have been applied. As a result, a lack of understanding and limited process control often lead to extensive sample losses of up to 90%. Because oxidation in air would be a controllable and enviromnentaUy friendly process, selective purification of carbon nanomaterials, such as CNT and ND, in air is very attractive. In contrast to current purification techniques, air oxidation does not require the use of toxic or aggressive chemicals, catalysts, or inhibitors and opens avenues for numerous new applications of carbon nanomaterials. 

For an industrial-scale production of carbon nanomaterials, it is important to use a simple and environmentally friendly purification method to selectively remove sp -bonded carbon from nanodiamond and amorphous carbon from nanotubes with minimal or no loss of diamond or nanotubes. In contrast to current purification techniques, which usually use mixtures of oxidizing acids, controlled air oxidation does not require the use of toxic or aggressive chemicals, catalysts, or inhibitors, thus opening avenues for numerous new applications of carbon nanomaterials. 

In addition to the size, also the shape of NMs was shown to play a role in induction of toxicity. NMs made of the same material but in different shapes can be differently internalized into the cells, react with cell membranes, and produce different oxidative effects [6, 14]. Carbon nanomaterials with different geometric structures (single-walled carbon nanotubes [SWCNTs], MWCNTs, and fullerenes) were shown to exhibit quite different cytotoxicity and bioactivity in vitro [15]. The uptake of Au nanospheres and nanorods was also significantly different, illustrating the role of the shape on NM internalization [6, 48],... 

Toxicity of carbon nanostructures has not been disclosed or understood. While toxicity of fullerenes and CNT are still under debate, relevant studies on new carbon nanomaterials like NCD and graphene have not commenced. Toxicity of materials has a determinative impact on their ultimate application and use, and thus understanding toxicity of carbon nanostructures (both during manufacturing and use) is as imperative as medical application study. 

Herzog, E. et al. (2007) A new approach to the toxicity testing of carbon-based nanomaterials - the clonogenic assay. Toxicology Letters, 174 (1-3), 49-60. 

Keywords carbon nanotubes, biomaterials, biocompatibility, toxicity, nanomaterials... 

CNTs have been studied for cancer therapies despite the fact that these have been shown to accumulate to toxic levels within the organs of diverse animal models and different cell lines (Fiorito et al., 2006 Tong and Cheng, 2007). The molecular and cellular mechanisms for toxicity of carbon nanotubes have not been fully clarified. Furthermore, toxicity must be examined on the basis of multiple routes of administration (i.e., pulmonary, transdermal, ocular, oral, and intravenous) and on multiple species mammals, lower terrestrial animals, aquatic animals (both vertebrates and invertebrates), and plants (both terrestrial and aquatic). A basic set of tests for risk assessment of nanomaterials has been put forward (Nano risk framework). 

From the time of lijima s publication on carbon nanotubes, CNT [1] (which were probably discovered earlier [2]), the question of their toxicity remains of key importance. The practical use of these unique nanomaterials in biotechnology, molecular biology and medicine can naturally be complicated because of possible... 

However, the exceptional size-specific behavior of nanomaterials in combination with their relatively large surface-to-volume ratio might result in potential risk for human health and the environment [26-28]. For example, fullerene (C60) particles suspended in water are characterized by antibacterial activity against Escherichia coli and Bacillus subtilis [29] and by cytotoxicity to human cell lines [30]. Single- and multiwalled carbon nanotubes (CWCNTs and MWCNTs) are toxic to human cells as well [31, 32]. Nano-sized silicon oxide (Si02), anatase (Ti02), and zinc oxide (ZnO) can induce pulmonary inflammation in rodents and humans [33-35],... 

A detailed discussion of experimental in vitro and in vivo testing methodologies and results is not the purpose of this chapter. There are some comprehensive reviews covering this topic. For instance, the contribution by Oberdorster et al. [45] who have summarized recent data and highlighted gaps in this field two works [60, 61] review data on environmental and human effects of carbon nanotubes in relation to their properties a paper [62] that discusses toxicological endpoints of combustion-derived nanoparticles a review [63] of quantum dots toxicity an excellent review devoted to toxicity of particular nanomaterials classes by Borm et al. [26] and many others. 

A. Magrez et al., Cellular toxicity of carbon-based nanomaterials. Nano Lett. 6, 1121-1125 (2006)... 

Warheit, D. B., et al. (2004), Pulmonary bioassay toxicity study in rats with single wall carbon nanotubes, in Proc. of First International Symposium on Occupational Health Implications of Nanomaterials. 

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