Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Progress on detecting glucose levels in saliva

04.06.2014

Researchers at Brown have developed a new biochip sensor that that can selectively measure glucose concentrations in a complex fluid like saliva. Their approach combines dye chemistry with plasmonic interferometry. A dependable glucose monitoring system that uses saliva rather than blood would be a significant improvement in managing diabetes.

Researchers from Brown University have developed a new biochip sensor that can selectively measure concentrations of glucose in a complex solution similar to human saliva. The advance is an important step toward a device that would enable people with diabetes to test their glucose levels without drawing blood.


Dealing with the 1 percent

A plasmonic interferometer can detect glucose molecules in water. Detection of glucose in a complex fluid is more challenging. Controlling the distance between grooves and using dye chemistry on glucose molecules allows researchers to measure glucose levels despite the 1 percent of saliva that is not water.

The new chip makes use of a series of specific chemical reactions combined with plasmonic interferometry, a means of detecting chemical signature of compounds using light. The device is sensitive enough to detect differences in glucose concentrations that amount to just a few thousand molecules in the sampled volume.

“We have demonstrated the sensitivity needed to measure glucose concentrations typical in saliva, which are typically 100 times lower than in blood,” said Domenico Pacifici, assistant professor of engineering at Brown, who led the research. “Now we are able to do this with extremely high specificity, which means that we can differentiate glucose from the background components of saliva.”

The new research is described in the cover article of the June issue of the journal Nanophotonics.

The biochip is made from a one-inch-square piece of quartz coated with a thin layer of silver. Etched in the silver are thousands of nanoscale interferometers — tiny slits with a groove on each side. The grooves measure 200 nanometers wide, and the slit is 100 nanometers wide — about 1,000 times thinner than a human hair.

When light is shined on the chip, the grooves cause a wave of free electrons in the silver — a surface plasmon polariton — to propagate toward the slit. Those waves interfere with light that passes through the slit. Sensitive detectors then measure the patterns of interference generated by the grooves and slits.

When a liquid is deposited on the chip, the light and the surface plasmon waves propagate through that liquid before they interfere with each other. That alters the interference patterns picked up by the detectors, depending on the chemical makeup of the liquid. By adjusting the distance between the grooves and the center slit, the interferometers can be calibrated to detect the signature of specific compounds or molecules, with high sensitivity in extremely small sample volumes.

In a paper published in 2012, the Brown team showed that interferometers on a biochip could be used to detect glucose in water. However, selectively detecting glucose in a complex solution like human saliva was another matter.

“Saliva is about 99 percent water, but it’s the 1 percent that’s not water that presents problems,” Pacifici said. “There are enzymes, salts, and other components that may affect the response of the sensor. With this paper we solved the problem of specificity of our sensing scheme.”

They did that by using dye chemistry to create a trackable marker for glucose. The researchers added microfluidic channels to the chip to introduce two enzymes that react with glucose in a very specific way. The first enzyme, glucose oxidase, reacts with glucose to form a molecule of hydrogen peroxide. This molecule then reacts with the second enzyme, horseradish peroxidase, to generate a molecule called resorufin, which can absorb and emit red light, thus coloring the solution. The researchers could then tune the interferometers to look for the red resorufin molecules.

“The reaction happens in a one-to-one fashion: A molecule of glucose generates one molecule of resorufin,” Pacifici said. “So we can count the number of resorufin molecules in the solution, and infer the number of glucose molecules that were originally present in solution.”

The team tested its combination of dye chemistry and plasmonic interferometry by looking for glucose in artificial saliva, a mixture of water, salts and enzymes that resembles the real human saliva. They found that they could detect resorufin in real time with great accuracy and specificity. They were able to detect changes in glucose concentration of 0.1 micromoles per liter — 10 times the sensitivity that can be achieved by interferometers alone.

The next step in the work, Pacifici says, is to start testing the method in real human saliva. Ultimately, the researchers hope they can develop a small, self-contained device that could give diabetics a noninvasive way to monitor their glucose levels.

There are other potential applications as well.

“We are now calibrating this device for insulin,” Pacifici said, “but in principle we could properly modify this ‘plasmonic cuvette’ sensor for detection of any molecule of interest.”

It could be used to detect toxins in air or water or used in the lab to monitor chemical reactions as they occur at the sensor surface in real time, Pacifici said.

The work is part of a collaboration between Pacifici’s group at Brown and the lab of his colleague Tayhas Palmore, professor of engineering. Graduate students Vince S. Siu, Jing Feng, and Patrick W. Flanigan are coauthors on the paper. The work was supported by National Science Foundation (CBET-1159255, DMR-1203186 and HRD-0548311) and the Juvenile Diabetes Research Foundation (JDRF Grant 17-2013-483).

Editors: Brown University has a fiber link television studio available for domestic and international live and taped interviews, and maintains an ISDN line for radio interviews. For more information, call (401) 863-2476.

Kevin Stacey | Eurek Alert!
Further information:
http://news.brown.edu/pressreleases/2014/06/glucose

Further reports about: blood detecting dye enzymes grooves interferometers levels measure nanometers propagate saliva sensitivity

More articles from Life Sciences:

nachricht Biology in a twist -- deciphering the origins of cell behavior
31.03.2015 | National University of Singapore

nachricht Speech dynamics are coded in the left motor cortex
31.03.2015 | Universitätsmedizin Göttingen - Georg-August-Universität

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Experiment Provides the Best Look Yet at 'Warm Dense Matter' at Cores of Giant Planets

In an experiment at the Department of Energy's SLAC National Accelerator Laboratory, scientists precisely measured the temperature and structure of aluminum as...

Im Focus: Energy-autonomous and wireless monitoring protects marine gearboxes

The IPH presents a solution at HANNOVER MESSE 2015 to make ship traffic more reliable while decreasing the maintenance costs at the same time. In cooperation with project partners, the research institute from Hannover, Germany, has developed a sensor system which continuously monitors the condition of the marine gearbox, thus preventing breakdowns. Special feature: the monitoring system works wirelessly and energy-autonomously. The required electrical power is generated where it is needed – directly at the sensor.

As well as cars need to be certified regularly (in Germany by the TÜV – Technical Inspection Association), ships need to be inspected – if the powertrain stops...

Im Focus: 3-D satellite, GPS earthquake maps isolate impacts in real time

Method produced by UI researcher could improve reaction time to deadly, expensive quakes

When an earthquake hits, the faster first responders can get to an impacted area, the more likely infrastructure--and lives--can be saved.

Im Focus: Atlantic Ocean overturning found to slow down already today

The Atlantic overturning is one of Earth’s most important heat transport systems, pumping warm water northwards and cold water southwards. Also known as the Gulf Stream system, it is responsible for the mild climate in northwestern Europe. 

Scientists now found evidence for a slowdown of the overturning – multiple lines of observation suggest that in recent decades, the current system has been...

Im Focus: Robot inspects concrete garage floors and bridge roadways for damage

Because they are regularly subjected to heavy vehicle traffic, emissions, moisture and salt, above- and underground parking garages, as well as bridges, frequently experience large areas of corrosion. Most inspection systems to date have only been capable of inspecting smaller surface areas.

From April 13 to April 17 at the Hannover Messe (hall 2, exhibit booth C16), engineers from the Fraunhofer Institute for Nondestructive Testing IZFP will be...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

World Conference On Regenerative Medicine 2015: Registration And Abstract Submission Now Open

25.03.2015 | Event News

University presidents from all over the world meet in Hamburg

19.03.2015 | Event News

10. CeBiTec Symposium zum Big Data-Problem

17.03.2015 | Event News

 
Latest News

Biology in a twist -- deciphering the origins of cell behavior

31.03.2015 | Life Sciences

Wrapping carbon nanotubes in polymers enhances their performance

31.03.2015 | Materials Sciences

Research Links Two Millennia of Cyclones, Floods, El Niño

31.03.2015 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>