Radio waves turn injected carbon into heat bombs against tumours.
Cancer cells can be destroyed from within, by injecting them with nanotubes and then zapping the tubes with radio-frequency waves.
Steven Curley at the University of Texas M. D. Anderson Cancer Center in Houston and his colleagues have taken the first step in proving the technique by injecting carbon nanotubes into liver tumour cells in rabbits, then heating up the carbon with radio waves to kill the cancerous cells. Similar work has been done in cultured cells, but this is the first time that the technique has been used in tumours in live animals.
Researchers are keen to find a form of radiotherapy that is more selective than those currently used on in cancer treatment, as the high-energy radiation also kills off some innocent cells, causing hair loss and other more serious symptoms.
One way to do this is to find a material that reacts to a frequency of radiation that leaves the rest of the body alone. If this material is embedded in cancerous cells, then only the cancerous cells would be targeted. Carbon nanotubes have been used before because, unusually, they can absorb near-infrared radiation, which penetrates human tissue without causing damage.
But near-infrared can only penetrate the top four centimetres of tissue or so, making deeper cancers impossible to reach. Radio waves don't have this issue. “Radio waves pass through us with no problems,” says Curley.
The work, published online in Cancer 1, was started by Richard Smalley of Rice University in Houston, Texas, who shared the 1996 Nobel Prize in Chemistry for his co-discovery of clusters of 60 carbon atoms, called C60. (Nanotubes are tubes of carbon wrapped up between two caps made of half a C60 sphere each.) Smalley died from cancer in 2005.
Too hot to handle
The researchers first injected a solution of carbon nanotubes into a liver tumour in a rabbit, and fired radio waves at the site for two minutes. This killed the cancer cells with nanotubes inside them, and the radio waves caused just a small amount of damage to some close-by, healthy cells.
The work is intriguing, says Hongjie Dai, from Stanford University in Palo Alto, California, who is using near-infrared radiation with nanotubes in similar systems in mice. “If indeed effective, it would be more desirable than the near-infrared laser heating method,” he says.
But Dai says that the reasons why the nanotubes get so hot need more investigation before the system can be advanced. “The physics behind the radio-frequency heating is not clear,” he says.
In test experiments, a suspension of nanotubes in water got as hot as 45ºC within 25 seconds when treated with radiofrequency waves. “I was really amazed by the amount of heat that was released by these nanoparticles,” says Curley.
He attributes the phenomenon to the “unique electronic properties” of carbon nanotubes. It might also be that the tubes align themselves into antennae-shaped arrangements to conduct heat better. Curley says that he has as-yet-unpublished evidence to better explain his findings.
One way to do this is to find a material that reacts to a frequency of radiation that leaves the rest of the body alone. If this material is embedded in cancerous cells, then only the cancerous cells would be targeted. Carbon nanotubes have been used before because, unusually, they can absorb near-infrared radiation, which penetrates human tissue without causing damage.
But near-infrared can only penetrate the top four centimetres of tissue or so, making deeper cancers impossible to reach. Radio waves don't have this issue. “Radio waves pass through us with no problems,” says Curley.
The work, published online in Cancer 1, was started by Richard Smalley of Rice University in Houston, Texas, who shared the 1996 Nobel Prize in Chemistry for his co-discovery of clusters of 60 carbon atoms, called C60. (Nanotubes are tubes of carbon wrapped up between two caps made of half a C60 sphere each.) Smalley died from cancer in 2005.
Too hot to handle
The researchers first injected a solution of carbon nanotubes into a liver tumour in a rabbit, and fired radio waves at the site for two minutes. This killed the cancer cells with nanotubes inside them, and the radio waves caused just a small amount of damage to some close-by, healthy cells.
The work is intriguing, says Hongjie Dai, from Stanford University in Palo Alto, California, who is using near-infrared radiation with nanotubes in similar systems in mice. “If indeed effective, it would be more desirable than the near-infrared laser heating method,” he says.
But Dai says that the reasons why the nanotubes get so hot need more investigation before the system can be advanced. “The physics behind the radio-frequency heating is not clear,” he says.
In test experiments, a suspension of nanotubes in water got as hot as 45ºC within 25 seconds when treated with radiofrequency waves. “I was really amazed by the amount of heat that was released by these nanoparticles,” says Curley.
He attributes the phenomenon to the “unique electronic properties” of carbon nanotubes. It might also be that the tubes align themselves into antennae-shaped arrangements to conduct heat better. Curley says that he has as-yet-unpublished evidence to better explain his findings.
Gannon, C. J. et al. Cancer doi: 10.1002/cncr.23155 (2007).
Source : Published online 5 November 2007 Nature doi:10.1038/news.2007.218
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