CLOSE

New Skin Patch Monitors Glucose and Delivers Diabetes Drugs

The wearable sweat monitoring patch on the skin. Image Credit: Hyunjae Lee and Changyeong Song

 
People with diabetes need to closely monitor their blood glucose levels multiple times every day, usually using a device that pricks their finger for a blood test to assess whether they need insulin shots or other drugs. Since blood collection and shots can be painful, not all patients do it as regularly as they need to—which can lead to dangerous fluctuations in their blood glucose levels.

Researchers have worked for years on methods to improve and even automate blood glucose monitoring and insulin/drug delivery. For example, insulin pumps make drug delivery easier, and recently designed artificial pancreas systems offer closed-loop monitoring and drug delivery. Now, researchers in Korea have just developed a wearable, and potentially disposable, glucose monitoring and drug-delivery system that uses sweat, not blood, to determine glucose levels.

The results, published today in Science Advances, suggest it’s a major upgrade. There are several differences between the artificial pancreas and the sweat-based monitoring system, according to lead author Hyunjae Lee, of Seoul National University in the Republic of Korea. While both devices can check blood glucose in real time and deliver necessary drugs, the artificial pancreas’s drug-delivery needles are permanently embedded subcutaneously, and the device itself is made of rigid plastic, which "might cause discomfort," Lee tells mental_floss.

The sweat-based system, on the other hand, is transfer-printed onto a thin silicone skin patch. It’s made of flexible and stretchable electronics, a series of stretchable graphene sensors—humidity, glucose, pH, and temperature—packed as closely as possible. The sensors’ electrodes are made from porous gold nanoparticles, whose structure helps create an electrochemically active surface area in order to analyze what’s in your sweat. Above a heating strip, which helps create humidity and generate sweat more quickly, is a film strip of drug-loaded microneedles, 0.6 inches by 0.8 inches. These are loaded with metformin, a drug used to control glucose in Type 2 diabetes. (At present, the sweat-based patch has not been tested on insulin, whose molecules are too big for delivery through the microneedles, though Lee hopes to work on designing one that can work with insulin in the future.)

Detail of the wearable sweat-analysis sensors. Image Credit: Hyunjae Lee and Changyeong Song

 
Sweat accumulates in the porous sweat-uptake layer of the patch, which also helps screen out negatively charged molecules, including drugs that may interfere with the glucose sensing. A waterproof band helps prevent the patch from peeling away from the skin. When the sweat covers the glucose and pH sensors, the measurements begin. "When blood glucose is high, [the] therapeutic part activates microneedle-based drug delivery," automatically, Lee explains.

Researchers adhered the patch to five healthy human subjects, ages 20 to 60. It takes 10–15 minutes for the device to generate enough sweat to measure glucose levels, though exercise could speed that process up. However, Lee says they took into account that for some people with diabetes, "sweat generation through exercise could be a burden." He adds, "Considering [that] point, we miniaturized sensor design that allows for reliable sweat analysis even with an infinitesimal amount of sweat."

The participants’ blood glucose levels were tested using a commercial glucose meter one hour before and after a meal as a comparison. The researchers found that the sweat-glucose sensor measurements were comparable to those of a commercial blood glucose assay kit.

Human clinical trials are not yet scheduled for the drug-delivery process, so to test this part of the system, Lee’s team turned to mice. They took 16 diabetic mice, 8 to 12 weeks old, and fasted them overnight before the experiment. They attached drug-loaded microneedles to their shaved abdomens, which had been stained with a special blue dye. Then, they used an embedded heating element to activate the microneedles, since the mice can’t produce enough sweat to do so. The microneedles' successful penetration of the skin was made visible by the blue dye.

The experimental groups of mice that received the drug delivery of metformin showed a significant decrease in blood glucose levels compared to the control groups that did not receive the drug. "In the animal experiment, we could confirm that blood glucose was continuously decreased and continued for six hours after microneedle therapy," Lee says.

While the system shows great success, Lee acknowledges there are adjustments to be made. "The sensor should be more sensitive and reliable to enhance accuracy of sweat-based glucose monitoring system," he says. In order to control the amount of drug delivered, they will also need to study "the correlation between sweat and blood glucose levels more thoroughly."

Despite the need for further research, Lee feels their device "can surely contribute to improve the quality of life of diabetic patients."

nextArticle.image_alt|e
Karen Bleier, AFP/Getty Images
arrow
Medicine
Bill and Melinda Gates Will Repay Nigeria's $76 Million Polio-Fighting Loan
Karen Bleier, AFP/Getty Images
Karen Bleier, AFP/Getty Images

Not long after announcing a $100 million donation to find a cure for Alzheimer's disease, Bill and Melinda Gates have agreed to pay off Japan's $76 million loan to Nigeria to stamp out polio, Quartz reports.

Polio has been eradicated in most countries around the world, but it's still present in Nigeria, as well as in Afghanistan and Pakistan. In 2008, according to The Conversation, Nigeria accounted for 86 percent of all polio cases in Africa. This high number was thanks in part to low immunization rates and calls from extremists to boycott polio vaccinations out of fear that they were tainted with anti-fertility steroids.

National and international campaigns were launched to lower polio rates in Nigeria, and in 2014 the nation received the loan from Japan to boost disease-fighting efforts. Progress has been made since then, with no new cases of polio reported in Nigeria in 2017. Two children had contracted polio in 2016, two years after Nigeria's last known case.

Nigeria's loan repayments to Japan were slated to begin in 2018. The Bill & Melinda Gates Foundation agreed to cover the costs after Nigeria met its goal of "achieving more than 80 percent vaccination coverage in at least one round each year in very high risk areas across 80 percent of the country's local government areas," Quartz reports. The loan will be repaid over the next 20 years.

While the Gates Foundation is lending a hand to Nigeria, the Associated Press reports that health officials in Pakistan's eastern Punjab province recently launched a new chapter in the nation's ongoing struggle against the disease. Health workers will engage in a week-long, door-to-door vaccination campaign, though efforts like this are risky due to threats from the Taliban and other militant groups, who view vaccinations as a Western conspiracy and believe they sterilize children. Anti-polio efforts in Pakistan also suffered after the CIA used vaccinations as a cover to get DNA samples from the Bin Laden compound.

[h/t Quartz]

nextArticle.image_alt|e
George Mayerle, U.S. National Library of Medicine // Public Domain
arrow
Design
This 1907 Vision Test Was Designed for People of All Nationalities
George Mayerle, U.S. National Library of Medicine // Public Domain
George Mayerle, U.S. National Library of Medicine // Public Domain

At the turn of the 20th century, San Francisco was a diverse place. In fact, Angel Island Immigration Station, located on an island in the San Francisco Bay, was known as the “Ellis Island of the West,” processing some 300,000 people coming to the U.S. in the early 1900s. George Mayerle, a German optometrist working in the city at the time, encountered this diversity of languages and cultures every day in his practice. So in the 1890s, Mayerle created what was billed as “the only [eye] chart published that can be used by people of any nationality,” as The Public Domain Review alerts us.

Anticipating the difficulty immigrants, like those from China or Russia, would face when trying to read a vision test made solely with Roman letters for English-speaking readers, he designed a test that included multiple scripts. For his patients that were illiterate, he included symbols. It features two different styles of Roman scripts for English-speaking and European readers, and characters in Cyrillic, Hebrew, Japanese, and Chinese scripts as well as drawings of dogs, cats, and eyes designed to test the vision of children and others who couldn't read.

The chart, published in 1907 and measuring 22 inches by 28 inches, was double-sided, featuring black text on a white background on one side and white text on a black background on the other. According to Stephen P. Rice, an American studies professor at Ramapo College of New Jersey, there are other facets of the chart designed to test for a wide range of vision issues, including astigmatism and color vision.

As he explains in the 2012 history of the National Library of Medicine’s collections, Hidden Treasure [PDF], the worldly angle was partly a marketing strategy on Mayerle’s part. (He told fellow optometrists that the design “makes a good impression and convinces the patient of your professional expertness.”)

But that doesn’t make it a less valuable historical object. As Rice writes, “the ‘international’ chart is an artifact of an immigrant nation—produced by a German optician in a polyglot city where West met East (and which was then undergoing massive rebuilding after the 1906 earthquake)—and of a globalizing economy.”

These days, you probably won’t find a doctor who still uses Mayerle’s chart. But some century-old vision tests are still in use today. Shinobu Ishihara’s design for a visual test for colorblindness—those familiar circles filled with colored dots that form numbers in the center—were first sold internationally in 1917, and they remain the most popular way to identify deficiencies in color vision.

[h/t The Public Domain Review]

SECTIONS

arrow
LIVE SMARTER
More from mental floss studios