AsianScientist (Mar. 21, 2017) – A research group from the Center for Nanoparticle Research within the Institute for Basic Science has developed a convenient and accurate sweat-based glucose monitoring and maintenance device. Their findings have been published in Nature Nanotechnology.
Conventional diabetes treatment requires painful and repetitive blood draws and insulin shots. Reluctance to comply with treatment can aggravate the symptoms of diabetes and even cause severe complications. Measuring blood glucose levels through sweat is a promising alternative, but existing enzyme-based systems are error-prone and may lead to drug overdoses.
Instead, a team of researchers led by Dr. Lee Hyunjae developed an easy-to-use, multistage module that can accurately monitor glucose levels in sweat. To speed up the sweat collection, the researchers designed the system to work under a small amount of sweat. The miniaturized sensor design allows for reliable sweat analysis even with 1 µl of sweat.
The researchers used electrochemically active, porous metal electrodes (replacing the graphene materials of the previous study) to enhance the sensitivity of the system. The porous structure also allows strong linkages among enzymes to form, resulting in increased reliability of the sensors under mechanical friction and deformation.
“It was quite a challenge to find the optimal size of the sensors. If the size is too small, the signal becomes too small or the surface functionalization becomes difficult to handle,” Lee said.
For more accurate reading and feedback therapy, the patch system incorporates an additional sweat uptake layer and a waterproof band. Because the sweat uptake layer consists of water-soluble and porous carbohydrate network, it can efficiently absorb the sweat exuding from the skin. Furthermore, the waterproof band behind the silicone patch facilitates the sweat collection and keeps the patch intact even under physical deformation of the skin.
The system also enables precise and timely drug delivery through the use of two different temperature-responsive phase change nanoparticles (PCNs). These nanoparticles are embedded in the microneedles, which are additionally coated with phase change materials. Once the system detects a high glucose level, the integrated heater modulates thermal actuation to activate either PCN1 alone or both PCNs. When the temperature reaches 40°C, only the drugs contained in PCN1 are released, whereas at 45°C, the drugs in both PCN1 and PCN2 are released.
“The previous systems cannot prevent natural diffusion of the drugs from drug reservoir, and rely heavily upon elevation of temperature to enhance the rate of drug diffusion. Our system uses PCMs to prevent drug release by using the melting properties of phase change materials above critical temperature, enabling stepwise drug delivery. Furthermore, different drugs can also be loaded in phase change nanoparticles for stepwise and multiple drug delivery,” Lee added.
The thermo-responsive microneedles controlled by three multichannel heaters can deliver the drug up to six steps of drug dosages in response to the measured sweat glucose level. The researchers confirmed that as more drug is delivered to the diabetic mice, the blood glucose level is suppressed more.
“This convenient and accurate system is also compatible for mass-production as it uses the metal electrode that can be easily fabricated via a conventional semiconductor fabrication process,” Lee said.
“Although there is still room for improvement before applying our system into the clinical application, this approach can surely contribute to improve the quality of life of diabetic patient by managing blood glucose more easily.”
The article can be found at: Lee et al. (2017) Wearable/Disposable Sweat-based Glucose Monitoring Device with Multistage Transdermal Drug Delivery Module.
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Source: Institute for Basic Science.
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