Carbon nanomaterials akin to asbestos
Nanomaterials that, by definition, have at least one dimension less than 100 nm are revolutionising components and devices in virtually every field. Their small size imparts very unique properties different from those of bulk quantities of the same materials. However, it is also the reason they may be particularly toxic to cells. Some studies suggest a similarity between MWCNTs and asbestos. However, in-depth knowledge of toxicity is lacking and engineered nanomaterials are still classified according to the toxicity of their bulk counterparts. Scientists launched the EU-funded project 'Toxicogenomic studies on engineered carbon nanomaterials' (MIRNANO) to compare effects of MWCNTs and asbestos on human bronchial epithelia cells with a focus on the role of microRNAs (miRNAs). MicroRNAs are small, single-stranded non-coding RNA molecules thought to regulate expression of RNA genes that have been transcribed from DNA but not yet translated into protein. They are particularly stable, making them a promising target for therapy. In parallel, development of in vitro and computational methods of evaluation was an important goal in line with efforts to reduce animal testing. The team conducted physicochemical studies of five different MWCNTs of varying geometries, a spherical carbon nanomaterial, asbestos (the positive control) and glass wool (the negative or non-toxic control). The two long, rod-shaped MWCNTs were the most cytotoxic. Advanced spectrometry showed that these two MWCNTs produced a unique, unidentified free radical whose presence was related to cytotoxicity in a dose-dependent manner. One of the MWCNTs, the so-called Mitsui-7 variant, has been shown to induce asbestos-like effects in human and animal cells. Scientists studied genome-wide changes in miRNA and RNA expression over a two-day exposure period. Using Mitsui-7 variant MWCNT, significant correlations were discovered between changes in messenger RNA/miRNA and mitochondrial dysfunction, resulting in preparation of a manuscript for publication. MIRNANO has shed important light on the cytotoxicity of an MWCNT commonly used in consumer products. The project has also highlighted ways to reduce and ultimately replace animal testing. The contributions will foster better regulation of engineered nanomaterials to prevent devastating diseases 20 years down the road.
