By Sara Miller, NoCamels -
The world’s most lethal animal is not the fierce lion, the mighty hippo or even the venomous snake, it is a tiny insect whose ability to spread deadly diseases outstrips even the most lethal of predators.
For it is the mosquito that kills more people than any other creature in the world, the US Centers for Disease Control says, by passing on diseases such as malaria, dengue, West Nile, yellow fever and Zika.
The energy humans expend fighting one another is “incomparable to the efforts we should put towards mosquito-borne diseases,” says Daniel Voignac, a researcher and PhD candidate at the Hebrew University of Jerusalem who has come up with a novel way to keep the insects away from our skin.
Mosquitos – of which there are more than 3,700 varieties – can be found in almost every part of the planet, and as global temperatures rise due to climate change, the warm and wet areas in which they thrive are only expected to increase, and with them the occurrences of the diseases they carry.
Safely and effectively preventing the insects from biting us remains a challenge. The most efficient repellents recommended by the US Environmental Protection Agency, such as DEET (diethyltoluamide), contain chemicals that a report published by the US government’s National Center for Biotechnology Information called “a silent environmental chemical toxicant.”
Voignac and his fellows at the Hebrew University have developed a cellulose-based gel that dries on the skin into what he calls “a really strong, transparent film,” which blocks mosquitoes from detecting the human scents that attract them to us.
Cellulose is a naturally occurring sugar compound made of carbon, hydrogen and oxygen that is found in plants, including fruits, vegetables and wood. It is used in industry in paper, adhesives and even cosmetics, and, although it is not water-soluble, the molecules in the film created by Voignac and his colleagues can be dispersed by water.
Voignac says the idea for the cellulose gel came during the coronavirus pandemic, when one of his two supervising professors at the Hebrew University, Yossi Paltiel, complained that he could not spend too long in his garden due to his susceptibility to mosquito bites.
That led to a conversation between Paltiel and Voignac’s other supervising professor, Oded Shoseyov, about combining their extensive scientific know-how and exploring ways to deter mosquitoes.
The group who came together to develop the cellulose gel – Paltiel, Shoseyov, Voignac, Prof. Jonathan Bohbot and PhD candidate Evyatar Sar-Shalom – were inspired by a rare study on the use of graphene, a newly discovered strong, transparent and conductive material made of a thin layer of carbon atom, as a potential mosquito repellent.
But they decided that graphene was not a viable option, despite the fact that its tight atomic structure does actually block a person’s scent from leaving the body.
“Mosquitoes would fly by and not detect anything,” Voignac tells NoCamels, calling graphene “chemical camouflage.”
“It’s a nice theoretical concept,” he says, “[but] it’s not that much of a scalable concept, because graphene has unknown toxicity.”
Furthermore, he explains, when it is scaled up in order to cover the skin, graphene takes on a dark color, rendering it unusable.
Instead, they turned to commonly used cellulose, whose properties Voignac was already exploring with relation to electrical engineering, as part of his PhD.
“We were working in the lab with [this] really cool material that is very thin, transparent and derived from plants,” Voignac says. “So we had knowledge of how to use this material.”
Tests of the cellulose gel – volunteers with it on their skin inserted a hand into a cage of mosquitoes – showed an 80 percent reduction in bites, which Voignac says was a “really nice” result.
Perhaps more crucially, they found that using the cellulose gel led to a 99.4 percent reduction in the number of eggs produced by the female mosquitoes used in the test, as they need human blood to create their eggs.
Only the female mosquitoes feed on humans to get the nutrients that are necessary to create the membranes of the eggs, Voignac explains.
“This also meant that we could create maybe an effective solution to prevent proliferation of mosquitoes,” he says.
At that point, the team approached Yissum, the Hebrew University’s tech transfer company, and patented their discovery. They also published a paper about their research in PNAS Nexus, a publication from the US National Academy of Science.
The paper made waves internationally, garnering coverage in dozens of news outlets worldwide and sparking the interest of what Voignac calls “industry leaders in mosquito repellents,” who were keen to learn more about the product. These are not, he stresses, the pharmaceutical companies, but rather cosmetics firms who are responsible for developing insect repellents for humans.
And because the US considers mosquito repellents to be pesticides, their impact on the human body is not regulated, he explains, and only their effect on the environment and the mosquitoes themselves must be evaluated. Furthermore, all of the components in the gel are established ingredients for cosmetics.
For now, the team is processing the data from its first round of tests, conducting further tests and refining a prototype of the gel.
If the prototype can be scaled up successfully and still work, then says Voignac they are “95 percent close to the final product.”
Through its collaboration with Yissum, the team is in contact with a number of companies interested in the gel, and Voignac is aware of its potential to reduce not only mosquito eggs and bites, but the diseases the insects can pass on to humans.
“We’re talking about malaria – it’s 1.16 deaths per minute,” he says.
“So it’s also a race against time; there’s a bigger issue than just a university lab trying to make money with a cool invention. If we have real technology, we want to race towards deploying it as fast as possible to the people that want it.”
