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Posted: Jul 20, 2011

How nanotechnology will transform disease detection

(Nanowerk News) Conventional diagnostic tools often cannot detect many cancers, Alzheimer's and other life-threatening diseases early enough to provide effective treatment. But nanotechnology, which is revolutionizing electronics and other fields, promises to similarly transform medicine, particularly when it comes to identifying illnesses more quickly.
In medicine, nanotechnology—the engineering of systems at the atomic or molecular scale to build devices that are exquisitely small—allows researchers to develop supersensitive materials composed of nanoparticles that are capable of recognizing disease markers at much lower concentrations than today's equipment can detect, meaning diseases can be caught and treated much earlier.
"Nanotechnology is changing the way the medical diagnostics field approaches disease detection," says Dr. Chad A. Mirkin, director of the Nanoscale Science and Engineering Center for Integrated Nanopatterning and Detection Technologies at Northwestern University. "The science has led to technology that has huge advantages in terms of detection, with highly sensitive ways of screening for diseases."
The National Science Foundation has supported the center with approximately $2 million annually for the past ten years. It is based at Northwestern, with research partners at the University of Chicago, the University of Illinois at Urbana-Champaign, and Argonne National Laboratory in Chicago, one of the Department of Energy's oldest and largest national labs for science and engineering research.
The screening technique involves creating arrays—an arrangement of molecular-sized spots on a chip or other surface--that are imprinted with specific antibodies or oligonucleotides (short strands of DNA) that interact with key disease markers that are present in, for example, a drop of blood. Because the spots are molecules, and not visible, scientists then treat the array with a solution of nanoparticles—in this case, gold—that turns the spots red if the telltale signs of disease are there.
"If you put a drop of blood on the chip, the right marker will go to the right spot. The molecules will reach out and grab the disease markers if they are present," Mirkin explains. "But you can't see it because it's a molecule. If you treat the chip with these gold particles, the gold particle will go to the spots where the marker is positive. When the markers are present, they will turn red in color."

Moreover, nanogold will do something that bulk gold cannot do. It will create a photograph developing solution on the chip that increases the signal, that is, the color, by 100,000-fold in less than five minutes. Put another way, the disease marker becomes 100,000 times more sensitive than that of conventional methods.

"These types of techniques are allowing researchers and medical doctors to look at disease markers that cannot be studied with conventional tools," says Mirkin, who also is professor of chemistry, medicine, chemical and biological engineering, and materials science and engineering. "The radar is much more sensitive than what we have currently, which means we can see diseases earlier and intervene earlier."

Also, the technology could help predict—earlier—those individuals who can consider themselves cured of cancer, as well as those likely to experience a recurrence. "With prostate cancer, for example, the high sensitivity allows you to measure rising PSA (prostate specific antigen) levels after surgery which may not be detectable using today's methods," Mirkin says. "It allows you to tell someone years earlier that he won't die, or it can predict a recurrence."

Early versions of the technology already are in commercial use, Mirkin says. And the research offers the real possibility of finding diseases that now are almost impossible to detect until it is too late.

In recent years, for example, Mirkin and his collaborator William Klein have developed an ultra-sensitive method using nanotechnology that could lead to a clinical test capable of diagnosing Alzheimer's disease in its earliest stages, instead of after death. They found a biomarker in living humans associated with the disease that apparently is present long before plaques and tangles show up in the brain, and before the signs of dementia become obvious.

Using bio-bar-code amplification technology, which Northwestern scientists invented in 2003, they detected miniscule amounts of a toxic protein in human cerebrospinal fluid, Amyloid ß-derived diffusible ligands or ADDLs (pronounced "addles"), that may be responsible for the early neurological deterioration in Alzheimer's disease.

The bio-bar-code amplification technology is a powerful nano analytical tool that can detect both proteins and DNA, as well as identify trace amounts of anthrax lethal factor and PSA. Potentially, it also could target known biomarkers for a wide variety of diseases, including HIV, cancer and Creutzfeldt-Jakob disease, a degenerative neurological disorder.

Nanotechnology "is going to be everywhere," Mirkin says, adding: "Creating highly sensitive ways of screening for diseases is going to change the way the medical profession operates, and will make a tremendous difference in the outcome for millions of patients."

Source: By Marlene Cimons, National Science Foundation
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