Carbon nanotubes pass in-vivo test

Tests show that carbon nanoparticles injected into the bloodstream of laboratory animals are rapidly expelled from the system.

While there has been some research done into the health consequences of ingesting nanoparticles, much of the public discussion extrapolates from known problems due to dusty substances such as asbestos fibres.

We know that a mass of very fine particles can lead to a greater inflammatory response than the same amount of larger particles, and that nanomaterials can pass easily into the body through the lungs, but is the asbestos analogy legitimate, and what exactly happens to nanoparticles once they get into the bloodstream?

In the first experiments of their kind, researchers from Rice University and the MD Anderson Cancer Center have carried out in-vivo tests on single-walled carbon nanotubes, to see how they behave in the bodies of laboratory animals.

Time-dependence of blood serum carbon nanotube concentration after injection into laboratory rabbits. The solid curve is a first-order kinetic fit to the data.

The research findings, which are published in the Proceedings of the National Academy of Sciences, show that on sampling tissue from a dozen organs 24 hours after directly injecting carbon nanotubes into the bloodstream of rabbits, significant amounts of nanotubes are found only in the liver, as one would expect if the particles were being expelled from the animals’ bodies. Trace amounts are found also in the kidneys, which are another natural expulsion route for waste products.

Rice University’s Bruce Weisman explains that disaggregated nanotubes have dimensions in the range of bio-macromolecules. “This is much smaller than asbestos particles, and would lead to quite different biological effects,” he explains. “For example, we found that the nanotubes became surrounded by natural blood proteins shortly after injection into the bloodstream. They were then apparently recognised by cells in the liver that remove extraneous objects from the blood, leading to nanotube accumulation in liver tissue.”

Weisman’s Anderson Center colleague Steven Curley adds that the research team are planning further tests to assess any long-term toxicity from the material: “We also plan to complete more-detailed pharmaco-kinetic studies including confirmation of renal clearance of the nanotubes.”

Article first published in Nanomaterials News.