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Nanospheres leave cancer no place to hide
21 June 2007
NewScientist.com news service
Celeste Biever
GOLD-coated glass "nanoshells" can reveal the location of tumours and then destroy them minutes later in a burst of heat.

Using these particles to detect and destroy tumours could speed up cancer treatment and reduce the use of potentially toxic drugs. It could also make treatment cheaper, says Andre Gobin of Rice University in Houston, Texas, who helped to create the particles.

In 2003 Gobin's supervisor Jennifer West showed that gold-coated silica nanospheres could destroy tumours in mice, while leaving normal tissue intact. The blood vessels surrounding tumours are leakier than those in healthy tissue, so spheres injected into the bloodstream tend to accumulate at tumour sites. Illuminating the tumour with a near-infrared laser then excites a "sea" of loose electrons around the gold atoms via a process called plasmon resonance. This creates heat, killing all the nearby cells.

However, before this can happen doctors first have to make sure they find all the tumour sites, which requires an MRI or CT scan. This extra stage can mean multiple hospital visits and more drugs for the patient.

Now the team has shown how to tweak the size of the nanoshells so that they also scatter some of the radiation. That means any cancer sites will "light up" under low-intensity infrared, so they can then be zapped with the laser. "We can use one single particle to accomplish two tasks and neither feature is diminished greatly," says Gobin.

To achieve this, the team had to carry out a delicate balancing act. Smaller spheres convert more radiation to heat, which makes them better at destroying tumours, but larger ones scatter more radiation, which is vital for the imaging stage. Previously, the spheres were 120 nanometres in diameter, which meant they only scattered 15 per cent of the light shone on them, and converted the rest to heat. West's team increased their size to 140 nanometres, causing them to convert 67 per cent of the light to heat, and to scatter the remaining 33 per cent.

The team injected the new particles into mice with colon carcinoma tumours and used a technique called optical coherence tomography to test their ability to act as an imaging agent. This involves shining low-power near-infrared light onto the tissue and then measuring where the scattered light bounces back. They found that the nanoparticles caused tumour tissue to light up 56 per cent more strongly than healthy tissue.

The team then applied a higher-power infrared laser to each tumour site for 3 minutes to heat the tissue. After a few weeks, they found the tumours had been almost completely destroyed. Eighty per cent of the mice treated survived for more than seven weeks, while all the control mice, who did not receive the nanoshells, died after three weeks.

Since optical coherence tomography only penetrates up to 2 millimetres, the imaging step will only be useful for locating tumours near the surface, such as cervical, mouth and skin cancers, says Gobin. However, the team plans to modify the nanoshells so that they work with more deeply penetrating radiation, such as X-rays. Houston-based Nanospectra Biosciences, which West co-founded, will begin trials of the spheres in humans in the next two months.

From issue 2609 of New Scientist magazine, 21 June 2007, page 28

Printed on Thu Jun 21 21:16:15 BST 2007

[lou_lou]

Create a back-up copy of your immune system
23 June 2007 From New Scientist Print Edition. Subscribe and get 4 free issues.
Andy Coghlan
IMAGINE having a spare copy of your immune system on ice, ready to replace your existing one should you fall victim to AIDS, an autoimmune disease, or have to undergo extensive chemotherapy for cancer.

An Anglo-American company called Lifeforce has received permission from the US Food and Drug Administration to do just that. The firm collects 480-millilitre samples of blood from healthy individuals, extracts the white blood cells and stores them as an insurance policy against future disease. The service comes at a price, though: around $800 for taking the initial sample then $25 per month for storing the cells at -196 °C. "That sample would have the complete repertoire of all your white blood cells," says Del DelaRonde, co-founder of Lifeforce in Newport, UK.

By taking some of the stored cells and exposing them to natural growth factors such as interleukin-2, whole new armies of white blood cells could be grown in the lab and reinfused into the patient. Many people with cancer undergo similar "adoptive" therapies using immune cells extracted before they have chemo- or radiotherapy, which can destroy immune cells. But there is a risk that the cells won't work optimally because of previous cancer damage, DelaRonde says. "Instead, we can send them their 'pristine' system from 25 years ago."

In the case of HIV, which progressively destroys immune cells, the process could be repeated perhaps once a year, by multiplying up and re-storing fractions of the samples.

"These things might be possible," says Francois Villinger of Emory University School of Medicine in Atlanta, Georgia. He previously showed that the progression of SIV infection, the monkey equivalent of HIV, could be delayed in macaques by using a similar approach. Whether it will work in humans is unknown, he says.

Also, some types of white blood cell, such as macrophages, may not survive freezing as well as others, meaning there may be a limit to the number of cells you could regenerate from the samples.

Last month, Lifeforce also won permission to expand its UK operations.

From issue 2609 of New Scientist magazine, 23 June 2007, page 8

Printed on Thu Jun 21 21:19:49 BST 2007