New device uses nanotubes to track asthma

Alexander Star, a chemistry professor in the University of Pittsburgh’s School of Arts and Sciences, is leading a team in developing a sensor that could detect an asthma attack before its onset.

Asthma is a reaction to certain stimuli that irritate the respiratory system, and the symptoms of asthma range from mild to life threatening.

In particular, an asthma sufferer could negatively respond to an environmental stimulant (or allergen), cold air or emotional stress, according to the World Health Organization.

An intense episode of asthma is called an asthma attack. During an asthma attack, the bronchial tubes in the respiratory system become inflamed with mucus. Because the airway is clogged, a person may experience wheezing, shortness of breath, chest tightness, and coughing.

Star’s device is a nanotube sensor that detects increases of nitric oxide in a person’s breath. Nitric oxide (NO) is a gas that is highly concentrated in the breath of asthma sufferers. The nitric oxide present in asthma sufferers is at least double the normal range.

Star stated in an e-mail, “Healthy individuals are in the range of 6.0–22.0 parts per billion of nitric oxide, while those affected by asthma are 40.0–80.0 parts per billion.”

To detect NO levels in a person’s breath, Star’s team used carbon nanotubes in their device. Carbon nanotubes are small wires whose diameters are 100,000 times smaller than a strand of human hair.

Carbon nanotubes can change their electrical conductivity when exposed to chemicals. To make their carbon nanotubes specifically sensitive to nitric oxide, Star and his team coated the tubes with a polyethylene imine polymer and added a gas converter and a carbon dioxide scrubber.

“The use of polyethylene imine polymer and the gas converter make the carbon nanotube sensor more sensitive and selective for nitric oxide gas in conditions simulating human breath,” Star stated.

Brett Allen, the primary researcher for this project, worked on the detection of NO levels with nanotubes in the presence of other pertinent gases, such as CO2 and O2 during exhalation.

Allen stated in an e-mail, “CO2, in particular, is an interfering component in the detection of NO. By implementing a scrubber, I was able to quantitatively remove an amount of CO2 while allowing for the detection of NO.”

Jigme Sethi, a professor in the Division of Pulmonary, Allergy and Critical Care Medicine at the University of Pittsburgh Medical Center’s Montefiore University Hospital, plans to clinically test Star’s sensor.

In a University of Pittsburgh press release, Sethi stated, “High-levels — perhaps two-thirds over normal — [of nitric oxide] may precede an attack by one to three weeks, but possibly earlier depending on the asthma’s severity.”

Although the hand-held asthma sensor works similarly to current NO detection devices, the use of nanotechnology allows Star to make this sensor a hand-held device. A hand-held device will “enable asthmatic patients to perform nitric oxide measurements at home,” Star stated.

Sethi stated that measuring NO in asthma patients requires expensive machines that can only be found in outpatient clinics. According to Allen, a hand-held NO detector is reusable, portable, and has an inexpensive design.

Allen would like to see this device grow to be as popular as the glucose sensors for diabetes. Star stated that he would like to have every pharmacy carry it on their shelves. The ultimate goal is that “people can get relief from this terrible disease,” Allen stated.

As of right now, Star has only tested his idea using simulated human breath. In theory, he has proven that carbon nanotube sensors can be used to detect nitric oxide for asthma treatment.

Star stated that “further sensor development is required to take this invention to market and such devices would require approval from Food and Drug Administration before becoming commercially available.”