A technique that enables biologically active enzymes to survive the rigors of inkjet printing presents a promising alternative to routine blood screening exams faced by diabetic patients. The researchers used this approach to make disposable devices that can measure glucose concentrations in human saliva.

This inset-printed sensor holds promise for inexpensive and easy monitoring of chronic diseases. (Credit: KAUST)

Strips of pH-sensitive paper are commonly used to test whether a liquid is acidic or alkaline. Researchers are now working to apply similar principles to create paper sensors that quickly indicate disease biomarkers. Key to this approach is replacing traditional electronic circuitry in the sensors with low-cost plastics that can be manufactured quickly and in large quantities.

Using a commercial ink made from conducting polymers, the team printed microscale electrode patterns onto glossy paper sheets. Next, they printed a sensing layer containing an enzyme, glucose oxidase, on top of the tiny electrodes. The biochemical reaction between available glucose and the enzyme creates electrical signals easily correlated to blood sugar levels. Coating the sensor with a nafion polymer membrane that repels the negative charges present in most interfering species enabled measurement of only the relevant glucose levels in saliva samples from volunteers.

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