Use liquid lasers to find cancer genes

U. MICHIGAN (US) — A new technique could offer a better way to detect the slight genetic mutations that might predispose a person to a particular type of cancer or other diseases.

Researchers at the University of Michigan say using liquid lasers works much better than the current approach, which uses fluorescent dye and other biological molecules to find and bind to mutated DNA strands.

When a patrol molecule catches one of these rogues, it emits a fluorescent beacon. This might sound like a solid system, but it’s not perfect. The patrol molecules tend to bind to healthy DNA as well, giving off a background glow that is only slightly dimmer than a positive signal.


Laser emission is used to amplify the small difference in signals that are generated by the different strands after they bind with a molecular beacon. The conversion is similar to analog-to-digital. (Credit: Christopher Burke)

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“Sometimes, we can fail to see the difference,” says Xudong Fan, an associate professor in biomedical engineering and principal investigator of the study published in the journal Angewandte Chemie. “If you cannot see the difference in signals, you could misdiagnose. The patient may have the mutated gene, but you wouldn’t detect it.”

In the conventional fluorescence technique, the signal from mutated DNA might be only a few tenths of a percent higher than the background noise. With Fan’s new approach it’s hundreds of times brighter.

“We found a clever way to amplify the intrinsic difference in the signals,” Fan says.

He did it with a bit of backtracking.

Liquid lasers, discovered in the late ’60s, amplify light by passing it through a dye, rather than a crystal, as solid-state lasers do. Fan, who works at the intersection of biomedical engineering and photonics, has been developing them for the past five years. In his unique set-up, the signal is amplified in a glass capillary called a “ring resonator cavity.”

Last year, Fan and his research group found that they could employ DNA (the blueprints for life that reside in all cells) to modulate a liquid laser, or turn it on and off. His group is one of just a few in the world to accomplish this, Fan says. At the time, they didn’t have a practical application in mind. Then they had an epiphany.

“We thought, ‘Let’s look at the laser output. Can we see what’s causing the different outputs and use it to detect differences in the DNA?'” Fan adds. “I had an intuition, and it turns out the output difference was huge.”

The journal editors named this a “hot paper” that “advances knowledge in a rapidly evolving field of high current interest.”

The research was funded by the National Science Foundation. The university is pursuing patent protection for the intellectual property, and is seeking commercialization partners to help bring the technology to market.

More news from the University of Michigan: www.ns.umich.edu/new/