Biosensor Detects Glucose in Saliva and Tears

A new type of biosensor has been created that can detect minute concentrations of glucose in saliva, tears and urine and might be manufactured at low cost.

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.

Scientists at Purdue University (West Lafayette, IN, USA) invented the apparatus which in addition to diabetes testing, the technology might be used for sensing a variety of chemical compounds to test for other medical conditions. Each nanosheet petal contains a few layers of stacked graphene. The edges of the nanosheets have dangling, incomplete chemical bonds, defects where platinum nanoparticles can attach. Electrodes are formed by combining the nanosheet petals and platinum nanoparticles. Then the glucose oxidase attaches to the platinum nanoparticles. The enzyme converts glucose to peroxide, which generates a signal on the electrode.

The technology is able to detect glucose in concentrations as low as 0.3 µM far more sensitive than other electrochemical biosensors based on graphene or graphite, carbon nanotubes and metallic nanoparticles. The sensor is able to distinguish between glucose and signals from other compounds that often cause interference in sensors such as uric acid, ascorbic acid and acetaminophen, which are commonly found in the blood. Unlike glucose, those compounds are said to be electroactive, which means they generate an electrical signal without the presence of an enzyme. Glucose by itself does not generate a signal but must first react with the enzyme glucose oxidase. Glucose oxidase is used in commercial diabetes test strips for conventional diabetes meters that measure glucose with a finger pinprick.


Jonathan Claussen, PhD, the senior author of the study said, “It's an inherently noninvasive way to estimate glucose content in the body. Because it can detect glucose in the saliva and tears, it's a platform that might eventually help to eliminate or reduce the frequency of using pinpricks for diabetes testing. We are proving its functionality." Dr. Claussen added, “Because we used the enzyme glucose oxidase in this work, it's geared for diabetes, but we could just swap out that enzyme with, for example, glutamate 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 findings were published on August 15, 2012, in the journal Advanced Functional Materials.

Related Links:
Purdue University