More Nano Weapons To Fight Cancer

By Roland Piquepaille

In this article, the MIT Technology Review says that different new nanotools will help us to diagnose or kill cancerous tumors. 'Nanoshells' invented at Rice University could become an alternative to chemotherapy by killing only cancerous cells after injection into patients' bloodstream. And nanoparticles created at the University of Washington in Seattle could be used to noninvasively diagnose and treat brain tumors. Meanwhile, a biochemist from Brigham Young University has developed "a method for examining mutations in DNA to determine a person's genetic predisposition for developing cancer."

Let's start with the nanoshells, developed by Naomi Halas and Jennifer West at Rice University.

Nanoshells are microscopic concentric spheres with silica cores and gold shells. Gold gives Halas the thermal and optical response her treatment process requires, and the body generates no antibodies against it. By varying the size of the silica core and the thickness of the gold, Halas found she could "tune" the nanoshells to absorb light of different wavelengths. "For cancer treatment," she says, "infrared proved best because it penetrates the body the furthest."
In experiments, nanoshells are injected into an animal's bloodstream, where "targeting" agents applied to them seek out and attach to the surface receptors of cancerous cells. Illumination with infrared light "raises the cells' temperature to 55 degrees Celsius" and burns away the tumor, she says.
Halas is focusing her research on breast cancer. She hopes nanoshells will prove a viable alternative to chemotherapy, which kills both healthy and diseased cells, resulting in side effects like fatigue and hair loss. Nanoshells, by contrast, kill only cancer cells.

Here is a diagram showing how nanoshells are conjugated with antibodies to kill cancerous cells.

Gold nanoshells
"In the immunoassay procedure proposed by Halas and West, nanoshells are conjugated with antibodies that act as recognition sites for a specific analyte. The analyte causes the formation of dimers,which modify the plasmon-related absorption feature in a known way." (Credit: Nature, via this PDF document).

Nanotechnologies also permits to detect tumors.

Miqin Zhang, a materials scientist at the University of Washington in Seattle, is using her own brand of nanoparticles to noninvasively diagnose and treat brain tumors. She calls her creations "smart superparamagnetic nanoparticle conjugates." When injected into the bloodstream, these particles target tumors' cell receptors with agents known as ligands.
Zhang's nanoparticles are made from iron oxide, which becomes especially magnetic when placed in a magnetic field such as those used for magnetic resonance imaging. The particles therefore enhance the signal that tumors emit during an MRI, making them easier to locate at earlier stages of development.

Nanotechnologies can also provide new instruments for examining cancer.

Adam T. Woolley, an assistant professor of chemistry and biochemistry at Brigham Young University, has created a method for examining mutations in DNA to determine a person's genetic predisposition for developing cancer. He uses a technique called atomic force microscopy (AFM), a nanoscale variation on old record players -- but with a needle tip only about 10 nanometers across. Woolley first deposits DNA molecules on silicon or mica, the surfaces of which are so flat that the DNA protrudes above them. Then, he explains, he uses AFM "to examine the topography of the DNA to locate the positions of mutations in it."

Will these new tools be largely deployed in the future? Only time will tell. At least, they're favorably welcomed by the scientific community.

Sources: John Harney, for Technology Review, April 30, 2004; and various websites

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