Raman effect makes cancer detection possible

April 21st, 2011 - 3:45 pm ICT by IANS  

Bangalore, April 21 (IANS) Scientists have found a method to detect cancer by combining the use of gold nanoparticles with Raman spectroscopy - a technique developed by Indian physicist C.V. Raman seven decades ago.

The research by Sanjiv Gambhir and colleagues at Stanford University in the US reported in Thursday’s Science Translational Medicine moves nanomedicine one step closer to reality.

Gold-silica nanoparticles - that are several thousand times smaller than the thickness of human hair - combined with Raman spectroscopy can safely detect colorectal cancer, according to their study done in mice.

They believe that their tiny gold balls — coated with materials designed to be detected with a Raman spectroscope — for finding colorectal and possibly other cancers would be ready for human trials within a year and a half.

The gold nanoparticles have little hook-shaped peptides that latch onto cancer cells, while any free-floating nanoparticles wash away. During an endoscopy, doctors can spot the cancer by seeing where the gold-silica nanoparticles have stuck.

In molecular imaging, molecules are injected into the body that home in on molecules that might be indicative of cancer. But once they home in on those molecules, they have to produce a large signal that can be detected outside the human body.

At Stanford, the researchers developed particles made out of gold that go into the bowel to detect colorectal cancer.

The gold acts as an amplifier to produce a very heavy or strong Raman signal from the gold particle after it has latched onto a colorectal cancer. The characteristic signals can be detected by a Raman spectroscope.

Nanoparticles of this type were originally used in currency inks to make them difficult to counterfeit. Embedded in currencies, the nanoparticles scatter light in unique patterns called Raman spectra when scanned for authenticity.

But Gambhir’s laboratory co-opted these gold-silica nanoparticles for a completely different use: bioimaging to detect colorectal cancer.

“Photoimaging with these nanoparticles holds the promise of very early disease detection, even before any gross anatomical changes show up, without physically removing any tissue from the patient,” a statement issued by the university quoted Gambhir as saying.

Currently, a promising way to catch cancer lesions early is to use fluorescent dyes coupled with antibodies that recognise and bind to cancer cells.

Magnetic resonance imaging (MRI) as well as computed tomography (or CT scanning) is some of the common imaging methods that are used to detect cancer. But these methods have different accuracies depending on what type of cancer one is studying and where in the body one is looking.

Nearly all colorectal cancers begin as small lumps of abnormal tissue called ‘polyps’ that line the intestine or rectum. Right now, doctors can view larger polyps during an endoscopy, but they often miss small or flat polyps.

But by having the gold nanoparticles light up literally wherever the cancer cells might be hiding in the bowel, “now the hope is that the endoscopist will be able to act on a lesion they would have otherwise missed,” the scientists said.

However, until now there has been no proof these nanoparticles won’t be toxic. The new study is the first-ever successful demonstration of their safety, according to the scientists.

Gambhir and colleagues examined the safety aspects by administering gold-silica nanoparticles directly into the intestine and by injection into veins.

The team monitored over 100 animals for two weeks. In both instances, the gold-silica nanoparticles were found to be safe at the doses tested.

The team is currently working on studying the safety of gold-silica nanoparticles in dogs. Eventually, patients may be able to simply drink the gold nanoparticles, the researchers say.

The tiny gold balls will settle in the stomach, travel into the bowel and latch onto cancer cells, allowing for real-time detection and diagnosis during an endoscopy.

(Killugudi Jayaraman can be contacted at killugudi@hotmail.com)

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