In the middle Ages, sometimes a smile appeared adjoining European folklore and children’s tales: Woe to that child who when he kisses his forehead has a salty taste. He is bewitched and will soon have to die. A salty-headed newborn was a frightening sign of a mysterious illness. The diagnosis of witchcraft was not maintained, of course, but today researchers think the salty taste warned of the genetic disease we now know as cystic fibrosis.
Cystic fibrosis affects more than 30,000 people in the United States and more than 70,000 worldwide. Mutations in the CFTR gene alter cell planes to make protein tunnels for chloride ions. The negative charge of chlorine attracts water, so that without too much chloride meandering towards the cells, the mucus in the body becomes thicker and stickier, making it difficult to breathe and often trapping dangerous bacteria in the cells. lungs. It also alters digestive enzymes that come out of the pancreas and into the intestine, causing inflammation and malnutrition.
Salty sweat is a telltale sign. Sometimes doctors meet with children 10 times higher levels of chloride in sweat than expected. Since the 1960s, measuring chloride has given doctors the clearest diagnoses: they stimulate people’s sweat glands, absorb as much as they can, and send samples to labs. But the tools are expensive, bulky, and hard to adapt to twisting babies. Sometimes tests do not collect enough fluid for a diagnosis. And if the test fails, often the parents and baby have to wait a couple of weeks to return.
“This failure to collect enough sweat only delays time until diagnosis,” says Tyler Ray, a mechanical engineer at the University of Hawaii at Mānoa who develops portable biosensors. This means wasting precious weeks in which doctors could prescribe treatments. It also creates a barrier for people who need to drive for hours — or fly over the oceans — to get to a hospital that can do the test. “There aren’t many in the whole country,” Ray says. “In fact, Hawaii doesn’t have any for the general population.”
Ray’s team of engineers and pathologists believe they have an alternative: sticky sweat collectors. In a study published last week in Barcelona Scientific translational medicine, report the creation of a malleable coin-sized sticker that changes color as it absorbs progressively higher salt concentrations, indicative of cystic fibrosis. When tested on infants and adults, the stickers filled with more sweat than traditional devices and did so more quickly.
“This is an exciting technology and something very new,” says Edward Fong, a pediatric pulmonologist with Hawaii Pacific Health who did not participate in the study. Fong believes these adhesives will make the diagnosis of cystic fibrosis more accessible. If it gets regulatory approval, it says, “we don’t need to send our patients 2,500 miles away so they can test their sweat.”
“Facilitating sweat tests would be the obvious victory,” agrees Gordon Dexter, a 36-year-old Maryland man living with the disease. Dexter is a moderator of the Reddit r / CysticFibrosis community, where people sympathize with digestive difficulties and celebrate the triumphs over lung bacteria. “Sweat tests can be ambiguous or just hard to do, and that’s a recurring question I’ve seen,” Dexter says.
Ray has had his eye on sweat for years. In 2016, as a postdoctoral fellow, he joined John Rogers ’lab at Northwestern University, where researchers had been playing with performing sweat analysis on portable sensors. They wanted to create new devices with small channels, valves and dyes that could track body chemistry in real time. Shortly after Ray arrived, the lab released a paper demonstrating a portable sensor that could reveal glucose, lactate and chloride ion levels in sweat, as well as its pH. This study placed the sensors as monitors for athletes or military in training, and researchers tested it during a long-distance bicycle race. Technology caught a lot of attention: Ray later worked with sports teams like the Chicago Cubs and Gatorade has used this technology to sell his Gx Sweat Patch. In 2017, the patches were on display at the New York Museum of Modern Art and were used to promote hydration at the South by Southwest festival.