Chemistry resolves toxic concerns about carbon nanotubes
sciencedaily.com |
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, experts say. In a new
study, published January 15 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.
sciencedaily.com |
Professor
Kostas Kostarelos, Chair of Nanomedicine 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."
Source: University
College London
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