Carbon nanotubes, according to preliminary data, are not toxic
Single-walled carbon nanotubes have great prospects in biomedicine. They can be used as a means of delivering drugs, therapeutic proteins and oligopeptides and nucleic acids to cells, providing both the transfer of "therapeutic" genes and the suppression of the expression of "harmful" ones, as well as contrast agents and markers for visualizing processes occurring in a living organism and diagnosing tumors. At the same time, the question of the potential toxicity of such nanotubes remains unresolved.
A new step towards understanding how nanotubes affect a living organism is made in the work of S.Gambhir and his colleagues (M.L. Schipper et al., A pilot toxicology study of single-walled carbon nanotubes in a small sample of mice, Nature Nanotech. 3, Nature Nanotechnology 3, 216-221) from Stanford University (USA). The researchers studied the acute and chronic toxicity of single-walled nanotubes (OSNT) when injected into the circulatory system of mice. Preliminary studies on a small group of mice did not reveal the toxicity of functionalized OSNT for 4 months.
In the work, the effects of two types of nanotubes were studied – with non-covalent functionalization with polyethylene glycol (OSNT-PEG) as the "least toxic scenario" and with covalent functionalization of oxidized nanotubes with polyethylene glycol (OSNT-O-PEG) as the "most toxic scenario". Solutions with OSNT were administered intravenously; a saline solution was injected into the control specimen. Groups of 5 mice were used, in each group there were mice of the same sex, one of them was the test subject. The article states that the experiments were carried out in accordance with all applicable rules and recommendations for the use of animals.
The mice were constantly monitored. There were no changes in appearance, nor any peculiarities in the behavior of the animals that were injected. Regular measurements of physiological parameters, including blood pressure and cardiogram, as well as a complete biochemical blood test did not reveal statistically significant differences between the groups. The changes that occurred during all four months of the experiment in the organisms of both experimental and control animals did not differ and corresponded to normal age-related changes. The study of tissues taken from mice after the end of the experiment using histological methods, as well as atomic force microscopy and Raman spectroscopy showed that both OSNT-PEG and OSNT-O-PEG were preserved inside the macrophages of the liver and spleen; there were no signs of any pathology.
This is the first systematic study of the toxicity of intravenously injected nanotubes, however, due to the small number of animals studied, the authors consider it as a pilot. In addition, experiments were carried out on immunodeficient mice. For a thorough assessment of the toxicity of nanotubes, it is necessary to conduct experiments using a sufficiently large number of animals.
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05.06.2008