Photonic Crystal Nanolaser Biosensor Simplifies DNA Detection

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Newswise WASHINGTON, D.C., January 13, 2015 A simple method to sense DNA, as well as potential biomarker proteins of cancer or other diseases such as Alzheimers, may soon be within reach thanks to the work of a team of Yokohama National University researchers in Japan.

As the team reports in Applied Physics Letters, from AIP Publishing, they created a photonic crystal nanolaser biosensor capable of detecting the adsorption of biomolecules based on the lasers wavelength shift.

Equally impressive, the nanolaser biosensor enables detection of the surface charge from its laser emission intensity, which in turn can also be used to sense the adsorption of biomolecules. Using laser intensity to detect biomolecules is potentially less expensive than the fluorescent tagging or spectroscopy techniques typically used in biosensors because it is a simpler procedure.

When the team first set out to explore photonic crystal nanolaser sensors, they werent focusing on the intensity of the laser emission because its sensitive to the quality of the fabricated laser and, frankly, they didnt expect it to show sensing signals.

In the beginning we focused on wavelength behavior, but quickly noticed that [the laser emission] intensity is influenced by both pH and polymers, noted Toshihiko Baba, a professor in Yokohama National Universitys Department of Electrical and Computer Engineering. Our results were very reproducible and, interestingly, we found that the behaviors of the wavelength and intensity are independent.

The team was surprised by these results, which they discovered when they deposited a protective film of thin zirconium dioxide (ZrO2) over the device using atomic layer deposition, and then tried sensing in liquids of high or low pH and liquids containing charged polymers. The coating was necessary to protect the nanolaser from damage and unwanted wavelength drift.

The nanolaser device can sense surface charge because the surface charge changes the occupancy rate of electrons at the surface states in the semiconductor of the nanolaser, Baba explained. This modifies the semiconductors emission efficiency.

So far, the teams work is the first report of the detection of surface charges using such photonic sensors. It enables detection of the adsorption of biomolecules from the nanolaser biosensor both in terms of wavelength and intensity, Baba said. Since it involves different physical parameters, the researchers can examine the details of the biomolecules.

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Photonic Crystal Nanolaser Biosensor Simplifies DNA Detection