Diabetes can be a life-threatening disease if not closely monitored, and finding out if you have it typically requires a series of blood tests and medical analysis. But what if someone could find out if they have the disease simply by taking a breathalyzer test?
That’s the promise of a new sensor developed by chemists at the University of Pittsburgh through the use of nanotechnology, carefully honed chemistry, and computer modeling, Alexander Star, an associate professor of chemistry at Pitt and the lead investigator on the project. “Breath analysis is a noninvasive, rapid, and economic alternative to standard blood analysis,” he told us. “It can be viewed as an alternative tool for the diagnosis and monitoring of diabetes without the pain of the blood test.”
Diabetes can sometimes be detected via breath acetone, a fruity odor that will increase with high glucose levels. Starr and his team -- including graduate student Mengning Ding -- created a diagnostic tool for the disease focused on this biomarker. Ding embarked on a range of experimentation to develop the sensor, Star told us.
“(Ding) tried many nanoparticles and polymers to enhance the sensitivity and selectivity of carbon nanotube-based sensors to acetone vapors, before focusing on titanium dioxide nanoparticles,” he said. "It also took a significant experimental and theoretical effort to rationalize the optimal combination of carbon nanotubes with titanium dioxide nanoparticles.”
Ding also had help from Dan Sorescu, a research physicist at the National Energy Technology Laboratory, who performed computational modeling of the interfacial electronic coupling and acetone binding to model the sensing mechanism, Star said.
Key to how the sensor works are single-walled carbon nanotubes, or SWNTs, as Star referred to them -- composed of a single cylindrical layer of carbon atoms -- which can conduct electricity by interacting with different chemical or biological species. “As one-dimensional structures, electrons are confined to the exterior of SWNTs, making them extremely sensitive to perturbations in the local charge environment, where analyte molecules may donate or accept electrons,” he said.
The main challenge researchers faced in designing the sensor was increased SWNT sensitivity to acetone molecules, Star said. To do this, the team used different nanoparticles and polymers before deciding to focus on titanium dioxide nanoparticles. Titanium dioxide is an inorganic compound widely used in products such as makeup. The SWNTs act like skewers in the sensor to hold the titanium dioxide particles together.
“Our SWNT-TiO2 hybrid nanomaterials demonstrated high electrical sensitivity to acetone vapors (induced by UV light illumination),” Star said. “Our sensor device achieved the detection of acetone as low as 2 ppm, with a calculated detection limit of 0.4 ppm, sensitivities necessary for this application.” Using this method, the sensor can be activated with light to produce an electrical charge. Researchers then cooked the skewers in the sensor under ultraviolet light to measure acetone vapors.
Star and his team are working on a prototype of the sensor, with plans to test it soon. “In a typical clinical experiment, subjects are asked to blow into a disposable bag, which can be then tested in analytical lab using gas chromatography and mass spectrometry techniques,” he said. However, “the exact correlation of breath acetone with diabetic diagnostic parameters, such as blood glucose, is still under active clinical investigation,” he added, so it’s not conclusive when the tests may be used in real-world scenarios.