Sensors Developed to Detect Disease Markers in Breath

A small, thin square of an organic plastic that can detect disease markers in breath or toxins in a building's air could soon be the basis of portable, disposable sensor devices. A device that monitors ammonia in breath, a sign of kidney failure, has been demonstrated.

Different groups of scientists have tried using organic semiconductors for gas sensing, but the materials were not sensitive enough to detect trace levels of disease markers in breath. One group has realized that the reactive sites were not on the surface of the plastic film, but buried inside it.

Bioengineers at the University of Illinois Urbana-Champaign focused on ammonia as a marker for kidney failure. Monitoring the change in ammonia concentration could give a patient an early warning sign to call their doctor for a kidney function test. The material they chose is highly reactive to ammonia but not to other compounds in breath, but by changing the composition of the sensor, they could create devices that are tuned to other compounds. For example, the scientists have created an ultrasensitive environmental monitor for formaldehyde, a common indoor pollutant in new or refurbished buildings.

By introducing tunable nanopores (50–700 nm) to organic semiconductor thin films enhances their reactivity with volatile organic compounds by up to an order of magnitude, while the surface-area-to-volume ratio is almost unchanged. Mechanistic investigations show that nanopores grant direct access to the highly reactive sites otherwise buried in the conductive channel of the transistor. The high reactivity of nanoporous organic field-effect transistors leads to unprecedented ultrasensitive ultrafast, selective chemical sensing below the 1 ppb level on a hundred millisecond time scale, enabling a wide range of health applications.

Ying Diao, PhD, an assistant professor and lead investigator said, “We would like to be able to detect multiple compounds at once, like a chemical fingerprint. It's useful because in disease conditions, multiple markers will usually change concentration at once. By mapping out the chemical fingerprints and how they change, we can more accurately point to signs of potential health issues.” The study was published on May 2, 2017, in the journal Advanced Functional Materials.