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Northwestern University and Evanston's Only Daily News Source Since 1881

The Daily Northwestern

Northwestern University and Evanston's Only Daily News Source Since 1881

The Daily Northwestern

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NU scientists discover new DNA identifier

A Northwestern professor and a small group of graduate students have discovered a faster and more accurate method of DNA analysis that could improve detection of cancer and other diseases in hospitals worldwide, the group said Wednesday.

Their discovery — a new protein identifier called bio-bar-code amplification (BCA) — could detect cancer when it is in the earliest stages, aiming to prevent it from spreading, said chemistry Prof. Chad Mirkin, who leads the group and serves as director of NU’s Institute for Nanotechnology.

“This is a very big development and is going to bring a great deal of visibility to Northwestern and the field of nanoscience,” Mirkin said.

The group has been working on the project since last April and published its findings in the April 27 Journal of the American Chemical Society.

If BCA were to replace the current method of protein detection — called polymerase chain reaction (PCR) — in all doctors’ offices, solutions such as blood samples could be tested much more efficiently.

Although PCR only can test one solution at a time, BCA is capable of testing multiple solutions at once.

Doctors using PCR currently can test seven to 10 patients per week, but with BCA doctors could process more than 100 tests per day, said Jwa-Min Nam, a graduate student who also helped develop the idea of BCA.

“I think our method will eventually topple PCR,” Nam said.

According to Savka Stoeva, a post- doctoral associate and member of the group of scientists that discovered BCA, it takes PCR six hours to detect certain cancers, while BCA can do it in three.

The new BCA technology could be beneficial to post-surgical treatment.

“If doctors want to monitor (protein) levels in men after treatment (for prostate cancer), with BCA they can find small levels of proteins that current techniques cannot detect,” Stoeva said.

The discovery also may benefit research fields beyond cancer. According to Mirkin, when analyzing diseases such as Alzheimer’s and HIV, BCA is beneficial when researchers want to examine the most basic virus level.

The Alzheimer’s tests are in collaboration with neurobiology and physiology professors Bill Klein and Lester Binder of NU’s Feinberg School of Medicine.

The HIV tests were developed in conjunction with Prof. Steve Wolinsky in Feinberg.

When doctors test patients for cancer, certain proteins are markers that indicate cancer’s presence. Currently the most commonly used method for detecting these proteins is the Elisa method.

But with the Elisa method, the proteins can only be detected if there is a high concentration of the protein, said Stoeva, who was involved in the research. BCA can detect cancer faster and in its earlier stages, he said.

For example, prostate specific antigen (PSA), a protein, is a cancer marker both for prostate cancer in men and breast cancer in women. In men the current Elisa method is sufficient because the PSAs are in high concentrations. But women with breast cancer have much lower levels of PSA in comparison, Stoeva added.

The BCA system uses two probes, or parts: magnetic particles and gold nanoparticles that are attached to “bar code” DNA.

These two parts “sandwich” the specific protein being searched for because they both possess antibodies to that protein.

Scientists then place these “sandwiches” on a chip, or glass slide, where complimentary strands of the “bar code” DNA attached to more gold nanoparticles are added.

Since the gold nanoparticles only attach if the protein is present, all scientists must do is look for their presence.

This is done by pouring on a silver solution that when mixed with the gold nanoparticles produce silver. After doing this, if silver spots appear, the protein is present.

“Prof. Mirkin and his team’s continued work is something that really lends to the national stature of the university,” said Alan Cubbage, vice president for university relations.

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NU scientists discover new DNA identifier