Soon, saliva to detect glucose levels

How about checking glucose levels without drawing blood? In a ray of hope for diabetics the world over, researchers have developed a new biochip sensor that can selectively measure glucose concentrations in a complex fluid like saliva.

A dependable glucose monitoring system that uses saliva rather than blood would be a significant improvement in managing diabetes.

"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, an assistant professor of engineering at Rhode Island-based Brown University.

"Now we are able to do this with extremely high specificity, which means that we can differentiate glucose from the background components of saliva," he added.

The new chip makes use of a series of specific chemical reactions combined with plasmonic interferometry - a way 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.

Saliva is about 99 percent water but it is the one percent that is not water that presents problems.

"There are enzymes, salts and other components that may affect the response of the sensor. With this device, we solved the problem of specificity of our sensing scheme," Pacifici said.

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 next step 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 non-invasive way to monitor their glucose levels.

It could also 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 in a paper published in the journal Nanophotonics.