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A Wearable Sensor for Glucose Monitoring

Assembly and the transfer process of the ISF glucose wearable patchFor persons with diabetes mellitus (DM), monitoring and moderating their glucose (blood sugar) levels is critical to maintaining health and well-being. Aside from doctor-ordered blood tests, which tend to be scheduled only every few months, patients can perform daily assessments with blood glucose monitors, which measure glucose in a drop of blood. It’s a tried-and-true method, but requires a fingerstick, which may involve mild pain and is definitely annoying (at least over time).

In a paper published in   Analytic Chemistry , a team of nanoengineers and a physician at UC San Diego describe testing a noninvasive, skin-conforming, and disposable patch — like a temporary tattoo — that is capable of monitoring glucose levels in interstitial fluid (ISF) — the fluid found in the spaces around cells.

The biosensing patch, which would be applied to skin, consists of two components:

  1. A low-cost, mass-produced screen-printed electrode system that extracts interstitial fluid by reverse iontophoresis (Iontophoresis is used in medical devices to deliver medication through the skin using mild electrical currents. In this case, the patch extracts tiny samples of interstitial fluid for analysis).
  2. A printed three-electrode glucose biosensor. The team is working on an electronic interface to control monitoring and communicate data wirelessly.

Study co-corresponding author and principal investigator of the clinical trial,   Edward Chao, DO, clinical professor of Medicine at UC San Diego School of Medicine and a member of the Institute of Engineering in Medicine at UC San Diego, said clinical trials involving participants with and without DM demonstrated good correlation between blood glucose levels and ISF concentrations. The patch was able to dynamically monitor changing glucose levels after food consumption, and could be worn for up to eight hours with no evidence of skin irritation or discomfort.

The authors said future improvements include extending operation time, increasing testing frequency and investigating materials that would allow for increased miniaturization.

“Such a low-cost skin-conformal system could thus pave the way for next-generation noninvasive glucose-monitoring devices, combining further technological refinements with enhanced patient comfort, to facilitate improved glycemic control and compliance,” the authors wrote. “These advances can help engage patients and assist health care professionals to personalize DM management recommendations toward improved glycemic control, clinical outcomes, and quality of life.”

Above images: Assembly and the transfer process of the ISF glucose wearable patch. The screen-printed electrode system is transferred to a layer of adhesive tape. Afterward, the iontophoretic electrodes are placed on top of the adhesive layer, the cathode is placed on top of the screen-printed array, and the anode is set 1.5 centimeters away from the cathode. Next, a piece of agarose gel is placed on top of each electrode. The transfer process consists of placing the adhesive layer on the skin and removing the top layer of paper from the adhesive surface. Wrist pictures before transferring the sensing device onto the skin and three hours after removing the device.

— Scott LaFee