Recent Buzz about Nanotube toxicity

I am back to blogging after a long hiatus. The recent buzz about the toxicity of carbon nanotubes had my phone ringing all day with inquiries about its impact on my research and with it my future. The whole topic was started by a widely read daily USA news paper. The next day it was published in Indian newspaper (at least in Chennai). For those of you who is wondering why am i writing a blog on this topic, I am working on using Single-walled Carbon Nanotubes (SWNTs) especially the ultra-short form of them (US-tubes) for "Diapeutics" (Diagnosis+Therapeutics) applications. Before posting my views, i should say the paper was the first one to study the Mesothelial (Kind of cell membrane you could find in the Pleural (Chest) and Peritoneal (Abdomen) cavities )effects of carbon nanotubes and a neatly researched one as well. The authors on this paper have enough experience and expertise on this subject. "Mesothelioma" is a type of cancer caused by fiber like particles especially asbestos) . Since carbon nanotubes are known to be longer in length, they make a very good candidate for the studies. But the kind of carbon nanotubes they used were called multi-walled carbon nanotubes (MWNTs). These MWNTs have multiple layers of Graphene sheet as opposed to single sheet in the case of SWNTs. They are really long > 2 micron and broad with diameters ranging from 15 to 160 nm. Where as the ultra-short tubes we use for our studies are only 50 nm in length and 1.4 nm in diameter. And for all of my well wishers the study itself showed that if the CNTs are smaller they have a no harmful effects (Even though the two material are different). In addition, what ever studies we had so far showed that the SWNTs and US-tubes are non toxic and could be used for clinical applications. I personally feel that this observation would have no negative effect on the area of nanobiology or in the use of nanoparticles for imaging application (my field of research) as it will be very difficult to administer a micron length nanotube in to the body as obviously the 'frustrated phagocytosis' ("the inability of the immune system to completely engulf the foreign object" will take place and you could have very little success in cellular labeling as longer particles (>100 nm) are not the best of particles for higher loading efficiency. For those of you have not got the access to the original article, i am quoting the conclusion from the article published online (see the reference below) "As such, our study does not address whether CNTs would be able to reach the mesothelium in sufficient numbers to cause mesothelioma following inhalation exposure. Although the study suggests a potential link between inhalation exposure to long CNTs and mesothelioma, it remains unknown whether there will be sufficient exposure to such particles in the workplace or the environment to reach a threshold dose in the mesothelium. Intraperitoneal injection of long asbestos into the peritoneal cavity of rodents has been demonstrated to cause mesothelioma in the long term. However, our study did not address whether the mice exposed to long CNTs that developed inflammatory and granulomatous changes would go on to develop mesotheliomas. Neither did our study rule out the possibility that short CNTs may have some intrinsic pathogenicity by virtue of their particulate nature, which would not have been detected in the assays used here, which are specific for fibre effects. These are research questions that must be addressed with some urgency before the commercial use of long CNTs becomes widespread."

(Reference :
"Carbon nanotubes introduced into the abdominal cavity of mice show asbestos-like pathogenicity in a pilot study"Craig A. Poland, Rodger Duffin, Ian Kinloch, Andrew Maynard, William A. H. Wallace, Anthony Seaton, Vicki Stone, Simon Brown, William MacNee & Ken Donaldson. Published online: 20 May 2008; | doi:10.1038/nnano.2008.111; Nature Publishing group")