Tag Archives: Maurizio Prato

The yin and the yang of carbon nanotubes and toxicity

 

Illustration courtesy of the University College of London (UCL). Downloaded from http://www.ucl.ac.uk/news/news-articles/0113/130115-chemistry-resolves-toxic-concerns-about-carbon-nanotubes

Illustration courtesy of the University College of London (UCL). Downloaded from http://www.ucl.ac.uk/news/news-articles/0113/130115-chemistry-resolves-toxic-concerns-about-carbon-nanotubes

Researchers at the University College of London (UCL), France’s Centre national de la recherche scientifique (CNRS), and Italy’s University of Trieste have determined that carbon nanotube toxicity issues can be addressed be reducing their length and treating them chemically. From the Jan. 15,2013 news item on ScienceDaily,

In a new study, published January 15 [2013] 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 carbon atoms rolled up into hollow tubes just a few nanometres in diameter. Engineered carbon nanotubes can be chemically modified, with the addition of chemotherapeutic drugs, fluorescent tags or nucleic acids — 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 diagnostic agents 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 abdominal cavity 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 biological fluids without aggregation are able to result in safe, risk-free material.

Here’s a citation and link for this latest  research, from the ScienceDaily news item where you can also read the lead researcher’s comments about carbon nanotubes, safety, and unreasonable proposals to halt production,

Hanene Ali-Boucetta, Antonio Nunes, Raquel Sainz, M. Antonia Herrero, Bowen Tian, Maurizio Prato, Alberto Bianco, Kostas Kostarelos. Asbestos-like Pathogenicity of Long Carbon Nanotubes Alleviated by Chemical Functionalization. Angewandte Chemie International Edition, 2013; DOI: 10.1002/anie.201207664

The article is behind a paywall. I have mentioned long carbon nanotubes and their resemblance to asbestos fibres in several posts. The  Oct. 26, 2009 posting [scroll down about 1/3 of the way] highlights research which took place after the study where mice had carbon nanotubes injected into their bellies; in this second piece of research they inhaled the nanotubes.

ETA Jan. 21, 2013: Dexter Johnson gives context and commentary about this latest research into long multiwalled nanotubes (MWNTs) which he sums up as the answer to this question “What if you kept the MWNTs short?”  in a Jan. 18, 2013 posting on his Nanoclast blog (on the IEEE [Institute of Electrical and Electronics Engineers] website)

Carbon nanotubes, neurons, and spinal cords (plus a brief plug for the Isabelle Stengers talk being livestreamed today)

Mention scaffolds, nanotechnology, and cells and I think of tissue engineering. Michael Berger’s March 2, 2012 Spotlight essay, Exploring the complexity of nanomaterial-neural interfaces, on Nanowerk mentions all three. From the essay,

Carbon nanotubes, like the nervous cells of our brain, are excellent electrical signal conductors and can form intimate mechanical contacts with cellular membranes, thereby establishing a functional link to neuronal structures. …

Now, researchers have, for the first time, explored the impact of carbon nanotube scaffolds on multilayered neuronal networks. Up to now, all known effects of carbon nanotubes on neurons – namely their reported ability to potentiate neuronal signaling and synapses – have been described in bi-dimensional cultured networks where nanotube/neuron hybrids were developed on a monolayer of dissociated brain cells.

In their work, a team of scientists in Italy, led by professors Maurizio Prato and Laura Ballerini, used slices from the spinal cords of mice to model multilayer-tissue complexity. They interfaced these spinal segments to multi-walled carbon nanotube (MWCNT) scaffolds for weeks at a time to see whether and how the interactions at the monolayer level are translated to multilayered nerve tissues.

I found this part of the explanation a little easier to understand,

According to the team, interfacing spinal cord explants [cells removed from living tissue and cultivated in artificial media] to purified carbon nanotubes over a longer period (weeks) induces two major effects: First, the number and length of neuronal fibers outgrowing the spinal segment increases, associated with changes in growth cone activity and in fiber elastomechanical properties. And, secondly, the researchers point out that after weeks of MWCNT  interfacing, neurons located at as far as five cell layers from the substrate display an increased efficacy in synaptic responses – which could represent either an improvement or a pathological behavior – presumably mediated by ongoing plasticity driven by the neuron/MWCNT hybrids.

If this increased efficacy in synaptic responses should represent an improvement, it suggests to me that it could be helpful with spinal cord injuries at some point. The researchers themselves are not speculating that far into the future (from the Berger essay),

They [Prato and Ballerini] note that this is important because it exploits the design of artificial micro- and nanoscale devices that cooperate with neuronal network activity, thereby creating hybrid structures able to cross the barriers between artificial devices and neurons.

Taken in conjunction with today’s (March 5, 2012) earlier posting (Carbon and neural implants), it seems that there is a great deal of work being done to integrate ‘machine’ and flesh so we achieve machine/flesh. While I don’t believe that philosopher and chemist Isabelle Stengers will be addressing those specific issues in her  talk, Cosmopolitics, being livestreamed here later today (3:30 pm PST) from Halifax (Nova Scotia), she does touch on this,

Professor Stengers’ keynote address will examine sciences and the consequences of what has been called progress. Is it possible to reclaim modern practices, to have them actively taking into account what they felt entitled to ignore in the name of progress? Or else, can they learn to “think with” instead of define and judge?  [emphasis mine]

I don’t know what she means by ‘think with’ but it strikes me that it represents a significant shift of thought as it implies a relationship that is not separated (or bounded) in the ways we have traditionally observed. Defining and judging are made possible by the notion of separation (boundaries); machine and flesh have been viewed from the perspective of boundaries and separation; machine/flesh seems more like ‘thinking with’.