Sensor detects glucose in diabetics’ saliva, tears

A new type of bio-sensor can detect minute traces of glucose in saliva, tears and urine, doing away with pinpricks for diabetes testing.

“It’s an inherently non-invasive way to estimate glucose content in the body,” said Jonathan Claussen, former Purdue University doctoral student and now a research scientist at the US Naval Research Lab.

“Because it can detect glucose in the saliva and tears, it is a platform that might eventually help to eliminate or reduce the frequency of using pinpricks for diabetes testing,” said Claussen, the journal Advanced Functional Materials reports.

Claussen and Purdue doctoral student Anurag Kumar led the project, working with Timothy Fisher, Purdue professor of mechanical engineering; D. Marshall Porterfield, professor of agricultural and biological engineering; and other researchers at the university’s Birck Nanotechnology Centre, according to a Naval Lab statement.

“Most sensors typically measure glucose in blood,” Claussen said. “Many in the literature aren’t able to detect glucose in tears and the saliva. What’s unique is that we can sense in all four different human serums: the saliva, blood, tears and urine. And that hasn’t been shown before.”

The sensor has three main parts: layers of nanosheets resembling tiny rose petals made of a material called graphene, which is a single-atom-thick film of carbon; platinum nanoparticles; and the enzyme glucose oxidase.

Besides diabetes testing, the technology might be used for sensing a variety of chemical compounds to test for other medical conditions.

“Because we used the enzyme glucose oxidase in this work, it’s geared for diabetes,” Claussen said.

“But we could just swap out that enzyme with, for example, glutemate oxidase, to measure the neurotransmitter glutamate to test for Parkinson’s and Alzheimer’s, or ethanol oxidase to monitor alcohol levels for a breathalyzer. It’s very versatile, fast and portable.”

The technology is able to detect glucose in concentrations as low as 0.3 micromolar, far more sensitive than other electrochemical biosensors based on graphene or graphite, carbon nanotubes and metallic nanoparticles, Claussen said.