New device offers a simpler and potentially less expensive way to detect DNA and other biomolecules through changes in surface charge density or solution pH
A simple method to sense DNA, as well as potential biomarker proteins of cancer or other diseases such as Alzheimer’s, may soon be within reach – thanks to the work of a team of Yokohama National University researchers in Japan.
Toshihiko Baba/Yokohama National University
This image shows a top view of the group’s nanolaser, in which the center narrow slot (horizontal line) is the main part of the sensor. The periodic holes form a photonic crystal, and although the size of the holes appears to fluctuate they’ve been intentionally modified so the laser’s emission is effectively extracted to the top.
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 laser’s 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 weren’t focusing on the intensity of the laser emission because it’s sensitive to the quality of the fabricated laser and, frankly, they didn’t 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 University’s 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 semiconductor’s emission efficiency.”
So far, the team’s 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.
It also “enables detection of the adsorption by measuring only its intensity, which is a significant advantage compared to conventional methods,” Baba added.
One conventional biosensing method “relies on fluorescent labels that are functionalized to biomolecules in advance,” he elaborated. “We can easily see the target biomolecules by using photoexcitation, which is the de facto standard method used today in bioscience and medical diagnoses.” The downside? The functionalization process of the fluorescent labels is expensive.
For this reason, many research groups have developed label-free methods such as those using resonance in optical cavities and plasmonic states. However, these require spectral analyses using spectroscopy of wavelength or resonance optical angle – also expensive.
By contrast, the team’s nanolaser biosensor needs neither labels nor spectrometers if they use the intensity change. This greatly simplifies detection, which they’ve already demonstrated in the case of DNA.
Among the many potential applications for the nanolaser biosensor, the team hopes “to apply it to sensing DNA, biomarker proteins of cancer, Alzheimers, etc., from human bodily fluids such as blood – as a simpler procedure than any others before now,” noted Baba. “Next we’ll be investigating the sensitivity, selectivity, and stability of this phenomenon. If these issues can be cleared, it will move another step toward practical use.”
“Our research project, which runs from 2012 to 2016, ultimately targets the development of a photonic crystal nanolaser sensor for biomarker detection,” said Baba. “We’re working to further simplify and improve the sensor so that it will be ready for practical use within a few years.”
The team’s work is funded by a research grant from the Ministry of Education, Culture, Sports, Science, and Technology in Japan.
The article, "Simultaneous detection of refractive index and surface charges in nanolaser biosensors," is authored by Keisuke Watanabe, Yoji Kishi, Shoji Hachuda, Takumi Watanabe, Mai Sakemoto, Yoshiaki Nishijima and Toshihiko Baba. It will be published in the journal Applied Physics Letters on January 13, 2015 (DOI: 10.1063/1.4904481). After that date, it can be accessed at: http://scitation.aip.org/content/aip/journal/apl/106/2/10.1063/1.4904481
The authors of this paper are affiliated with Yokohama National University.
ABOUT THE JOURNAL
Applied Physics Letters features concise, rapid reports on significant new findings in applied physics. The journal covers new experimental and theoretical research on applications of physics phenomena related to all branches of science, engineering, and modern technology. See: http://apl.aip.org
Jason Socrates Bardi
American Institute of Physics
Jason Socrates Bardi | newswise
Studying fundamental particles in materials
17.01.2017 | Max-Planck-Institut für Struktur und Dynamik der Materie
Seeing the quantum future... literally
16.01.2017 | University of Sydney
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).
Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...
Many pathogens use certain sugar compounds from their host to help conceal themselves against the immune system. Scientists at the University of Bonn have now, in cooperation with researchers at the University of York in the United Kingdom, analyzed the dynamics of a bacterial molecule that is involved in this process. They demonstrate that the protein grabs onto the sugar molecule with a Pac Man-like chewing motion and holds it until it can be used. Their results could help design therapeutics that could make the protein poorer at grabbing and holding and hence compromise the pathogen in the host. The study has now been published in “Biophysical Journal”.
The cells of the mouth, nose and intestinal mucosa produce large quantities of a chemical called sialic acid. Many bacteria possess a special transport system...
UMD, NOAA collaboration demonstrates suitability of in-orbit datasets for weather satellite calibration
"Traffic and weather, together on the hour!" blasts your local radio station, while your smartphone knows the weather halfway across the world. A network of...
10.01.2017 | Event News
09.01.2017 | Event News
05.01.2017 | Event News
17.01.2017 | Earth Sciences
17.01.2017 | Machine Engineering
17.01.2017 | Physics and Astronomy