Raise awareness of environmental health issues in order to better protect our children and future generations.

EMF Studies

24 June 2016

Wearable Biosensors Studied for Clinical Monitoring and Treatment

Institute for Basic Science/Seoul National University
Attention!  These devices operate wirelessly and use nanotechnology and materials.  How safe are they for our health?

Wearable Biosensors Studied for Clinical Monitoring and Treatment
by Bridget M. Kuehn, MSJ
JAMA. Published online 23 June 2016 doi:10.1001/jama.2016.6240

Pricking a finger multiple times a day to monitor their blood glucose levels often proves overwhelming for patients with diabetes. Many simply won’t follow their physician’s recommendation to test so frequently, making it harder to manage their condition.

“It’s a lot of stress,” said Dae-Hyeong Kim, PhD, an associate professor in the School of Chemical and Biological Engineering at Seoul National University in Korea. “Many patients don’t want to do it every day so they will do it once a week or once a month, and that will aggravate their diabetes.”

Kim and his colleagues have been working to develop a noninvasive way to monitor blood glucose using a tiny wearable electronic biosensor that detects glucose levels in sweat. In fact, preliminary research demonstrated that their Band-Aid–sized device not only monitors sweat glucose, but also might be coupled with microneedles to deliver medication (Lee H et al. Nat Nanotechnol. doi:10.1038/nnano.2016.38 [published online March 21, 2016]).

The device is part of a new generation of flexible, wearable biosensors being developed worldwide as potential clinical tools. The devices build on the successes of the now ubiquitous wearable fitness trackers that measure activity, heart rate, and sleep using mobile technology. But they go a step further integrating advances in nanotechnology and materials science to detect clinically meaningful metabolites and other compounds in sweat and other bodily fluids.

“Mobile devices allow us to do this type of on-body monitoring,” said Joseph Wang, DSc, director of the Center for Wearable Sensors at the University of California, San Diego (UCSD). “It started with fitness and sports, but it is moving to biomedical applications.”

Kim’s group is one of many exploring wearable sweat-based biosensors to monitor blood glucose levels. Although there are minimally invasive continuous glucose monitors currently on the market, these devices require insertion of a sensor under the skin to measure interstitial glucose levels and wirelessly transmit this information to a pager-sized monitor (http://1.usa.gov/1WfP7rh).

Artificial pancreas systems that couple these minimally invasive glucose monitors with automated insulin pumps that dispense the appropriate doses of insulin are also in development (Hampton T. JAMA. 2014;311[22]:2260-2261). Advanced versions are moving toward the pivotal trials necessary to gain US Food and Drug Administration approval (Kropff J and DeVries JH. Diabetes Technol Ther. 2016;18[suppl 2]:S253-S263).

“The artificial pancreas systems still rely on minimally invasive [glucose monitoring] technology,” said Wang. “And they still need to be validated with a finger stick,” Wang noted.

Many researchers, like Kim, are looking to develop next-generation, noninvasive sweat-based wearable glucose monitors by building on evidence that the glucose content in sweat can be a faithful indicator of blood glucose (Moyer J et al. Diabetes Technol Ther. 2012;14[5]:398-402).

“You can remove the pain and stress [of needle sticks],” Kim said. “But at the same time, you have challenges that are different than blood-based glucose monitoring.”

Glucose levels in sweat are much lower than in the blood stream, so accurately measuring these levels is more difficult, Kim said. In addition, pH level, body temperature, and the amount of sweat can skew glucose measurements in sweat and must be adjusted for.

To overcome these challenges, Kim and his colleagues layered miniaturized electronic sensing systems for each of these variables onto their flexible adhesive patch. To test it, they adhered the patch to 2 healthy male volunteers and monitored their glucose levels using a mobile device application that wirelessly communicates with the glucose-sensing patch. The sweat glucose levels measured by the device matched measurements from a commercial glucose meter used on the men.

While the results are promising, Kim noted that there are still potential obstacles, including variations in the skin condition of individuals that could affect sweat collection.

“The beauty is it is noninvasive,” Wang said of sweat-based glucose monitoring. “But there are still questions about how clinically relevant [sweat glucose levels are].”

To circumvent this potential limitation, Wang and his colleagues have developed a tattoo-based glucose sensor that uses reverse iontophoretic extraction to draw glucose from the interstitial space without puncturing the skin (Bandodkar AJ et al. Anal Chem. 2015;87[1]:394-398).

“We want to do noninvasive glucose monitoring and get the same information [as the continuous glucose monitors],” Wang said.

Several groups of researchers are working to develop tear-based glucose sensors (Ascaso FJ and Huerva V.Optom Vis Sci. 2016;93[4]:426-434). For example, Novartis has licensed Google’s glucose sensing contact lens technology (http://bit.ly/1HJCJFP).

Preliminary data suggest that noninvasive glucose monitors might also be coupled with minimally invasive medication administration. For example, Kim and his colleagues tested whether metformin-loaded microneedles on their sweat-sensing patch could effectively deliver the drug to mice genetically engineered to have a diabetes-like condition.

“We want to administer the drug automatically and hopefully invisibly,” said Kim.

The patch was adhered to the shaved abdomen of the mice. Unlike the microneedle patches being studied to administer vaccines, which dissolve immediately when they contact the interstitial fluid, these microneedles were designed to dissolve when the patch is heated up. Kim explained that this would allow the patch to release insulin only when the insulin sensing data indicated a need. When the patches were heated, Kim and his colleagues showed that not only was insulin released, but the mice’s blood glucose decreased.

Clinical validation and commercialization are the next steps for Kim’s device.

“We need a lot of collaboration and cooperation with physicians,” Kim said.

Continue reading:

No comments:

Post a Comment