Honeybees can “smell” lung cancer

Float like a butterfly, sniff out cancer like a bee?

Honeybees can detect the subtle scents of lung cancer in the lab — and even the faint aroma of disease that can waft from a patient’s breath.

Inspired by the insects’ exquisite olfactory abilities, scientists hooked the brains of living bees up to electrodes, passed different scents under the insects’ antennae and then recorded their brain signals. “It’s very clear — like day and night — whether [a bee] is responding to a chemical or not,” says Debajit Saha, a neural engineer at Michigan State University in East Lansing.

Different odors sparked recognizable brain activity patterns, a kind of neural fingerprint for scent, Saha and colleagues report June 4 in Biosensors and Bioelectronics. One day, he says, doctors might be able to use honeybees in cancer clinics as living sensors for early disease detection.

Electronic noses, or e-noses, and other types of mechanical odor-sensing equipment exist, but they’re not exactly the bee’s knees. When it comes to scent, Saha says, “biology has this ability to differentiate between very, very similar mixtures, which no other engineered sensors can do.”

Scent is an important part of how many insect species communicate, says chemical ecologist Flora Gouzerh of the French National Research Institute for Sustainable Development in Montpellier. For them, “it’s a language,” she says.

The idea that animal senses can get a whiff of disease is nothing new; doctors reported a case of a border collie and a Doberman sniffing out their owner’s melanoma in 1989. More recently, scientists have shown that dogs can detect COVID-19 cases by smelling people’s sweat (SN: 6/1/22). A lot of insects probably have disease-detecting abilities, too, Gouzerh says. Ants, for instance, can be trained to pick out the smell of cancer cells grown in a lab dish. But until now, bees’ abilities haven’t been quite so clear, she says.

By plugging directly into insects’ neurons, scientists can bypass behavioral training. Instead of taking weeks to teach a dog to sit when it smells something suspicious, for instance, the team can get their answer straight from the brain.

Honeybees were held in place with 3-D printed plastic harnesses and some wax while the researchers performed bee brain surgery, attaching wires to the region that processes odors. A device delivered puffs of air to the insects’ antennae, like a salesperson spritzing scents at a perfume counter.

Each puff could contain a milieu of mingling odors, such as those exhaled by healthy people. Another mixture mimicked the miasma of lung cancer patients’ breaths, which contain distinct odors utterly undetectable to human noses. Using electrical signals read from the bees’ brains, researchers could distinguish between the two types of synthetic breath at least 93 percent of the time.

In a separate experiment, Saha’s team collected air lingering above lung cells grown in the lab. The bees could successfully tell the difference between air samples taken near healthy cells and those gathered near cells of two cancer types: small-cell lung cancer and non-small cell lung cancer.

Ongoing work in Saha’s lab has also revealed that bees’ smelling prowess extends to other trace scents, like those emitted by perfluoroalkyl and polyfluoroalkyl substances, commonly known as PFAS, or forever chemicals. “That actually blew my mind,” he says. “PFAS in the environment are very, very hard to detect.”

Saha’s team hopes to use their apian scent sensor to test the breath of actual cancer patients. The device’s biggest weakness is that it lasts just a few hours before the bees’ brain health wanes and responses become unstable, he says. But it works fast and spits out results in real-time. With just one bee brain, Saha says, his team could theoretically buzz through more than 100 samples.