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Nanotubes put cancer under the spotlight

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Marie Freebody, [email protected]

Blasting tumors with light from a laser is an experimental technique that has taken an important step forward, thanks to a team from Wake Forest University Baptist Medical Center. The researchers have shown for the first time that targeting tumor cells using nanoparticles that can be picked up on an MRI scanner leads to more accurate and efficient tumor zapping.

Their work builds on an approach known as laser-induced thermal therapy, in which laser energy is used to heat and destroy tumors. The laser light is directed at tumors injected with nanoparticles. These nanoparticles heat up under laser fire, subsequently heating and killing off the surrounding tumor cells.

The problem with the technique, however, is that while the tumor can be visible in a medical scan, the nanoparticles are not. Once injected, the nanoparticles cannot be tracked, which could lead to healthy tissue being destroyed if nanoparticles away from the tumor are zapped.

Xuanfeng Ding and his Wake Forest colleagues found that, by using multiwalled carbon nanotubes loaded with iron, they can bring the nanoparticles to life in an MRI scanner. The result is better targeting of the tumor cells for safer and more efficient cancer treatment.

This transmission electron microscopy image shows the presence of iron particles (black dots) in multiwalled carbon nanotubes. Images courtesy of Wake Forest University.

“Our approach has the potential to decrease the treatment time and laser energy as well as improve accuracy,” said Ding, who presented the work at the 52nd Annual Meeting of the American Association of Physicists in Medicine in Philadelphia on July 21. “Since the nanotubes are able to absorb laser energy so quickly and efficiently, and then transfer this energy into heat, they help to destroy the target with less laser energy.”

In fact, compared with traditional laser-induced thermal therapy, the laser energy required is about 10 times lower. According to Ding, simply blasting the tumor with a near-infrared laser for 30 seconds at a power of 3 W/cm2 means that only the tumor injected with the multiwalled carbon nanotubes will be zapped – such a low-power laser leaves healthy tissue unaffected.

This approach can be applied to any superficial tumor, including skin cancer and some lymphoma cancers that are at a depth of 1 to 2 cm. For deeper tumors, Ding suggests either inserting a small fiber into the target area or using a multibeam laser system.

Depicted here are structural magnetic resonance coronal images before (a) and after (b) the injection of a 600-mg ferrocene multiwalled carbon nanotube solution. The dark area shows the multiwalled carbon nanotubes inside the tumor.

At this stage, the team has successfully demonstrated its technique on mice bearing breast cancer tumors, but the group is optimistic that nanotubes will be the best candidate for future imaging and therapeutic all-in-one agents. “They have unique tiny hollow structures that could be filled with not only iron particles for imaging, but also with drugs for chemotherapy applications,” Ding said.

Since the nanotubes have not yet been tested on human patients, much work still needs to be done to rule out toxicity and to explore any long-term side effects.

“New materials’ toxicity is always a concern. A lot of research groups, including our own biology group, are working on the toxic study in vivo and in vitro,” Ding said. “To the best of our knowledge, these carbon-based nanoparticles are not toxic to mice, but in order to use them in humans, we need to conduct more experiments.”

Oct 2010
52nd Annual Meeting of the American Association of Physicists in MedicineBiophotonicsBioScancancerchemotherapyDingimagingironLaser-induced thermal therapyLITTMarie FreebodyMicroscopyMRImulti-beam laser systemmulti-walled carbon nanotubesMWCNTsnanoNewstoxicitytumorWake Forest Baptist University Baptist Medical CenterXuanfeng Dinglasers

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