Researchers hope that a "robot nose" could allow officers from kindergarten to 9th

Rudy of the Golden Retriever, wearing military ID plates and an American flag, is trained by the US military to use his incredible nose to find human remains.Credit: US Army

Every day, thousands of trained K9 dogs detect narcotics, explosives and missing persons across the United States. These dogs are priceless for safety, but they are also very expensive and can be tired.

Duke researchers took the first steps toward building an artificial "robot nose" device made from live mouse cells that agents could use instead of dogs.

The researchers developed a prototype based on odor receptors derived from mouse genes that respond to target odors, including cocaine odors and explosives. Their work appeared earlier this month in Nature Communications.

In fact, there are two or three big differences between testing items in a lab dish and testing them in a real nose.

"This idea of ​​artificial nose has been around for a long time," said Hiroaki Matsunami, lead author of the study, professor of molecular genetics and microbiology at the Duke School of Medicine. "The receptors were identified in the 1990s, but significant technical obstacles prevent the production of all these receptors and the monitoring of the activity so that we can use it in an artificial device."

Existing "electronic noses" are now using various chemical compounds to detect odors instead of the recipient's stem cells, Matsunami said. He said that these devices are "not as good as a trained dog".

"The idea is that by using existing live receptors, we may be able to develop a device similar to that of animals," said Matsunami. "Nobody has yet achieved this goal, but this study goes in that direction."

The genomes of humans, dogs and mice contain about 20,000 genes, which contain instructions for creating proteins that smell, taste, smell, move and do everything our body does. About five percent of the mouse genes have been identified as instructions for making odor receptors, said Matsunami. In contrast, humans only use about two percent of their genes to make odor receptors.

"These animals are investing a lot of resources for this purpose," said Matsunami. "Mice and rats smell very well; we simply do not use mice to detect explosives in real life. This poses some practical problems.

The first step in the study was to identify the best odor receptors to respond to target odors such as cocaine or marijuana.

The researchers created a liquid medium containing molecules able to illuminate as a result of reactions. Then, they copied about 80% of the mouse odor receptors and mixed them with seven targeted odor chemicals in the holder.

They measured the resulting luminescence and selected the best performing odor receptors for the second part of the study, which controlled the activation of the receiver in real time.

Previous research had exposed some receptors to odorous chemicals in a liquid. But there are several differences between the petri dish and the nose. On the one hand, we rarely immerse our noses in liquid baths containing odorous chemicals. Instead, our nose detects odors emanating from floating odors or foul odors. And our noses are full of mucus.

Thus, for the second part of the study, funded by the National Institute of Health grants DC014423 and DC016224, and the RealNose project of the Defense Advanced Research Agency, they attempted to replicate the way we use our noses by exposing odorants to vapors and enzymes.

The researchers tested the receptors they had identified for two odor vapors for this study.

"We only tested two of them in the newspaper, but that shows the proof of principle of how it can be used," said Matsunami.

The researchers hope to refine the device to test all receptors against many odors.

"We have a panel of receivers that allows us to monitor the different reaction of different odor receptors, including those with a similar chemical structure or that may be related to actual use, such as an element associated with explosives or drugs. "Said Matsunami.

The researchers also tested various enzymes present in the mucus to determine how they facilitated or prevented the reactions. This process is more realistic than vapor molecules in direct interaction with odor receptors.

"You would think that when we smell a chemical, it binds to the chemical receptor in the nose, but in reality it's not that simple," Matsunami said. "When the chemical dissolves in the nasal mucus before binding to the receptor, it can be converted to another chemical by enzymes contained in the nasal mucus."

Mucus is an unknown border in the understanding of our smell. Rebuilding key components of nasal mucus could be the next step toward building an artificial nose, according to the paper.

"It's not as if our paper would soon be applied to a portable device used in the airport, but it's an important step forward to show that it's possible," he said. said Matsunami. "We can more clearly see what kind of obstacles to overcome so that the community can create such a device."

Three of the authors ran a patent application for the work.

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