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.


        Presently only works extremely close to body surface.
        Work being done to extend depth.

        http://www.newscientist.com/article/mg19426096.500?DCMP=3DNLC-nlett=
er&nsref=3Dmg19426096.500


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.

=93Using one particle to detect and destroy tumours could cut treatment =

length=94
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.

-- =

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