Electronic Nose Smells Trouble

In the publishing industry some people have a nose for news. In the health field, there’s a new nose that’s looking for trouble. Semiconducting ceramic sensors covered in metal oxide fibers show promise as a diagnostic tool known as an e-nose that sniffs out health problems.

Like an alcohol breathalyzer, more sophisticated devices are being developed that can smell disease in the body. The human olfactory system inhales and transmits the pleasure of fresh flowers, meat cooking on the BBQ, and newly mowed grass. An e-nose (electronic nose) works with what you exhale. It can detect malaise caused by kidney disease, high cholesterol, diabetes or liver failure, not by what you breathe in, but by what you breathe out.

Breath has been used to indicate an individual’s health since ancient times. The sweet smell of a baby’s breath, the yucky smell of dog breath, even the foul breath of illness is something most of us have experienced. Now those smells are being analyzed not by humans, but by technology.

Obviously, our habits, food and drinks can reveal themselves in our breath. Onions, alcohol, cigars give themselves away. However, health-related smells are what the e-nose is concerned with.

Our breath exudes the result of our body’s metabolism in the form of. volatile organic compounds. The levels or mixtures of those compounds can indicate certain diseases. Acetone, for example, can be measured to determine if a diabetic requires more insulin. When the body does not have enough insulin, a hormone that is important in glucose metabolism, it instead uses fatty acids as an alternative source of energy. Acetone, a ketone, is a byproduct of that fat metabolism. Your breath will take on a fruity smell if there is a severe imbalance.

An asthma attack can be signaled by measuring nitric oxide. Isoprene could measure cholesterol levels and an ammonia smell emanating from your breath might indicate kidney disease. Ammonia mixed with ketones could signal disease in another organ, your liver. In the e-nose, the crystalline structure and atomic configuration on the surface of nanofibers are structured to detect certain compounds. The concentration of those compounds are shown on the e-nose’s digital display.

A Stony Brook University research team led by Associate Professor Perena Gouma focuses on selective chemical detectors, biosensors and hybrid nanoprobes for electronic olfaction systems and nanomedicine applications. They expect their small handheld device to come with a price tag of around only $20. Gouma’s research has simplified testing to a point where a single breath is all they need. In some circumstances, the e-nose could replace blood testing.

Each sensor in the array responds to a variety of odors.

Each sensor in the array responds to a variety of odors.

The Lewis Research Group, led by chemistry professor Nathan Lewis at the California Institute of Technology created a different system based on polymer films rather than nanoscale wires to identify compounds. It is made up of sensor arrays. The polymer film responds to a gaseous vapor by swelling which produces an increase in the electrical resistance of the film. The system is designed to mimic the human olfaction process using pattern recognition algorithms to identify odors. It works similar to the way our noses produce diagnostic patterns and sends them to our brain to process and identify.

Yet another chemistry professor, Edward Zellers at the University of Michigan School of Public Health is interested in small wireless chemical sensing equipment in relation to environmental health. His activities include sensing equipment to test indoor-air quality, monitor personal exposure, perform breath analysis, and to map ambient air pollution.

Sensitive equipment is being used to monitor both the air we inhale as well as the breath we exhale. E-noses that look for health conditions won’t become the latest fashion statement, but they may become an impressive tool in your doctor’s office in the future.