Progress on detecting glucose levels in saliva

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.

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.

Last week, we heard about Google’s attempt to measure glucose levels through contact lenses. Now imagine being able to check your glucose levels just by sticking a thermometer under your tongue for a few seconds.

Believe it or not, there’s a new company on the scene working on a diabetes device that would use nothing more than a bit of your spit to take a glucose reading.

It’s called the iQuickIt Saliva Analyzer (that’s a mouthful!) and it’s in development by Connecticut-based health startup Quick LLC, founded by two ER doctors and a diabetes specialist in that state.

Interest in non-invasive glucose testing has peaked recently among the public at large with the news of Google’s contact lens project and persistent rumors that Apple’s still working on a smartwatch that could that could moniiQuickIt Analyzer Metertor and display health sensor data including BG levels. And while many in the D-Community take news of new “pain free” testing methods with a grain of salt, it’s always interesting to see new ideas surfacing.