UC Riverside mosquitoes

Credit: SensoryGen

What if, rather than slathering yourself in potentially toxic DEET, you could arm yourself against mosquitoes with an effective, natural repellent that smelled mildly of grape and orange blossom? 

SensoryGen, an Encinitas, California startup launched by UC Riverside researchers, is developing new approaches to combatting mosquitoes that could offer protection from deadly diseases like Zika, dengue fever and malaria, while improving backyard barbecues everywhere.

UC Riverside entomology professor Anand Ray works with Sean Boyle, one of his graduate students. They are studying the sense of smell of insects and how that relates to the spread of insect-borne disease.
Credit: Lonnie Duka

Startup founders say they are about two years away from bringing to market a lotion made from naturally occurring plant-based compounds. The lotion is highly effective against mosquitoes, including Aedes Aegypti, which carries the Zika virus.

The product is based on a simple idea: employ compounds that smell good to people but gross to mosquitoes.

Just like humans, insects smell by means of sensory cells. Inside the cells are proteins that sense volatile compounds, and send a positive or negative signal to the brain.

In some cases, chemicals that activate positive responses in one species will trigger negative ones in another.

“Flies are regularly attracted to garbage, whereas we would rather avoid it,” said entomologist Anandasankar Ray, who runs the UC Riverside lab that produced the research and technology behind SensoryGen.

Ray and his colleagues hoped to find substances that would repel mosquitoes. But the challenge was finding the molecular needles in a haystack.

That’s where biology and bioinformatics grad student Sean Boyle came in. He created machine learning software that used training sets based on synthetic chemicals to learn the shapes of molecules that mosquitoes didn’t like.

How to make humans repugnant to bloodsucking pests

The machine then scanned tens of thousands of molecules to find naturally-occurring ones that triggered the same revulsion response; those results were further refined to pick out a few scents that humans found pleasing.

“We didn’t know which shapes fit into the receptors, but we had examples of the shapes of structures they didn’t like, and those they didn’t mind,” Boyle said. “We trained the computer to recognize the difference.”

Within a matter of hours, the computer was able to accomplish what could’ve taken years of trial and error in the lab.

Once researchers had a list of likely candidates, it was a matter of field-testing their results.

At Ray’s UC Riverside lab, researchers coated themselves in the various substances, then donned protective gloves and thrust their hands into a cage full of mosquitoes to see how the insects would react.

Most of the time the mosquitoes tried to eat them alive. But five compounds proved highly effective in putting the bloodsucking insects off their lunch.

Among them were substances approved by the FDA as safe enough to eat, including a food flavoring that is used in hard candy and Gatorade, and another flavor – derived from plums – often used in puddings and baked goods.

The natural substances proved to be as effective as high concentrations of DEET, the synthetic compound the CDC recommends as the best protection against Aedes Aegpyti. The trouble with DEET is that it relies on toxins that can cause side effects in humans.

“There is so little we can do quickly against these terrible diseases like Zika and dengue,” Ray said. “Drugs have to pass clinical trials.”

Because SensoryGen is developing products based on substances that have already been tested and approved as safe, the researchers expect their products can be brought to market quickly.

And repellents are just the start. Using the same machine learning technology, researchers are testing natural pesticides which are proving effective against pests like the spotted wing Drosophila, which feeds on fruit and causes hundreds of millions of dollars of crop damage worldwide.

“This technology can help us figure out, what are substances that can push away pest species in a natural and safe way?” said Boyle.