Chemistry resolves toxic concerns about carbon nanotubes

Jan 15, 2013
Chemistry resolves toxic concerns about carbon nanotubes

Safety fears about carbon nanotubes, due to their structural similarity to asbestos, have been alleviated following research showing that reducing their length removes their toxic properties.

In a new study, published today in the journal Angewandte Chemie, evidence is provided that the asbestos-like reactivity and pathogenicity reported for long, pristine nanotubes can be completely alleviated if their surface is modified and their effective length is reduced as a result of chemical treatment.

First atomically described in the 1990s, carbon nanotubes are sheets of rolled up into just a few nanometres in diameter. Engineered carbon nanotubes can be chemically modified, with the addition of , fluorescent tags or – opening up applications in cancer and gene therapy.

Furthermore, these chemically modified carbon nanotubes can pierce the cell membrane, acting as a kind of 'nano-needle', allowing the possibility of efficient transport of therapeutic and directly into the cytoplasm of cells.

Among their downsides however, have been concerns about their safety profile. One of the most serious concerns, highlighted in 2008, involves the carcinogenic risk from the exposure and persistence of such fibres in the body. Some studies indicate that when long untreated carbon nanotubes are injected to the of mice they can induce unwanted responses resembling those associated with exposure to certain asbestos fibres.

In this paper, the authors describe two different reactions which ask if any chemical modification can render the nanotubes non-toxic. They conclude that not all chemical treatments alleviate the toxicity risks associated with the material. Only those reactions that are able to render carbon nanotubes short and stably suspended in without aggregation are able to result in safe, risk-free material.

Professor Kostas Kostarelos, Chair of at the UCL School of Pharmacy who led the research with his long term collaborators Doctor Alberto Bianco of the CNRS in Strasbourg, France and Professor Maurizio Prato of the University of Trieste, Italy, said: "The apparent structural similarity between carbon nanotubes and asbestos fibres has generated serious concerns about their safety profile and has resulted in many unreasonable proposals of a halt in the use of these materials even in well-controlled and strictly regulated applications, such as biomedical ones. What we show for the first time is that in order to design risk-free carbon nanotubes both chemical treatment and shortening are needed."

He added: "Creative strategies to identify the characteristics that nanoparticles should possess in order to be rendered 'safe-for-use', and the ways to achieve that, are essential as nanotechnology and its tools are maturing into applications and becoming part of our everyday lives."

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More information: 'Asbestos-like pathogenicity of long carbon nanotubes alleviated by chemical functionalization' is published in the journal Angewandte Chemie on 15 January. onlinelibrary.wiley.com/doi/10… e.201207664/abstract

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katesisco
1 / 5 (1) Jan 15, 2013
Chemically altering long carbon nanos to short is good. What will happen when the altered (by chemicals) carbon nanos are put inside a bag of chemicals (the human body)?
So the true test of the safety of this altered carbon nano is to see if this chemical reaction does not regress/alter with time.
RealScience
5 / 5 (1) Jan 15, 2013
Another avenue to try would be to investigate the toxicity of much longer CNTs. Short-fiber asbestos is more hazardous than long-fiber asbestos, so long-enough nanotubes might also be safer than intermediate-length nanotubes.
that_guy
not rated yet Jan 15, 2013
@katesisco - covalent bond carbon (Diamond, bucky balls, graphene, CNT) are very stable and need very specific chemicals to alter them.

It is possible that a bodily chemical may alter them in an unwanted, toxic way, but unlikely. Also, we are judging the effect of CNTs empirically, reactively, in these experiments. So we can assume that if the short nanotubes don't react badly in the body, then they're probably not being affected in a harmful way by the body's chemicals.
that_guy
1 / 5 (1) Jan 15, 2013
Science can be frustrating because of the common population. There is all this fear of hugely toxic nanomaterials and the scientific apocalypse, fear of vaccinations, etc.

Yes, progress brings with it occasionally very terrible things (Asbestos, agent orange, unregulated x-ray use, etc) but as we become experienced with different breakthroughs, we are more aware of the risks and better able to test (CNTs aren't even in consumer products yet) and reduce unwanted risks.

Technology should not be feared. It should be respected with the appropriate amount of caution. If we didn't do things because of these possible risks, then we would still have an average life expectancy of 35 years.

I think history tells us, take your time and be careful with new materials, GM, biotech, and other breakthroughs - But by all means, proceed if you wish to move the world forward.
DonaldJLucas
not rated yet Jan 21, 2013
This article makes me wonder that if carbon nanotubes are similar structurally to asbestos that perhaps there is a possibility of chemically altering asbestos in a similar way to make it non-toxic or significantly less toxic? Asbestos has several very difficult to beat physical properties except for the fact that it can cause cancer and other biological difficulties.