NORTH CAROLINA—The fragrance of a rose comes from volatile organic compounds. Living plants, animals, humans and even inanimate objects emit complex mixtures of these compounds. VOC mixtures are so distinctive that new words are used to describe them: volatilome, breathprint and smellprint.
“There are over 2,000 VOCs in a person’s breath,” says scientist Dan Wilson. “If you have a disease, you release abnormal compounds in your breath. This allows pathologists to non-invasively detect many different diseases in the body by simply analyzing the breath.”
Similarly, sick bats can be diagnosed by their smellprints. Every bat species has a distinctive smellprint. Bats infected with the fungal pathogen Pseudogymnoascus destructans have different smellprints than healthy bats. P. destructans causes white-nose syndrome, a disease that has killed more than six million bats since 2006.
Electronic noses can differentiate P. destructans from related fungal species that grow on bat skins but are not pathogenic, as Wilson and his colleagues reported in the journal Sensors & Transducers.
Identifying the P. destructans smellprint signature is just the beginning. Molecule by molecule, Wilson and his colleagues are identifying the VOCs associated with different cave types, the P. destructans pathogen, white-nose syndrome and at least eight WNS-susceptible bat species. The scientists are also looking for VOC disease biomarkers.
Anna Doty, a post-doctoral research associate at Arkansas State University, is integral to this work. Doty’s winter field work includes riding to remote caves on a four-wheeler, collecting air samples with VOCs from bats, and shipping the air samples to Wilson’s WNS lab in Mississippi. Their collaboration is featured in an Untamed Science video.
E-noses can detect disease in a wide range of hosts—plants, animals and humans. Wilson’s review paper, published in the journal Chemosensors, shows how modified e-nose technologies, theories and methodologies can be applied to such varied hosts.
“E-nose technologies are advancing at an explosive rate,” says Wilson. New sensors, algorithms, methods and VOC-biomarkers are identified and developed every year. New smellprint databases are constantly being developed. Smellprint patterns are so precise that false negatives and false positives can be largely eliminated, especially when used with application-specific reference databases and disease biomarker detection. This science is still developing, but the possibilities are vast.