Featured image above: type-1 diabetes patch, which consists of wearable sensors (Humidity, Glucose, pH, Strain, and Temperature sensors) and a co-integrated feedback drug delivery system. Credit: Hui Won Yun, Seoul National University

Recent technological advances in painless, wearable electronic devices could help make life easier for diabetics and their carers.

To keep their blood sugar levels in check, diabetics need to draw blood from their fingertips to measure glucose concentration, and then calculate the amount of insulin they need to inject, several times a day. This is painful and tedious, and often leads to poor management, with dangerous consequences.

Type-1 diabetes is a lifelong disease, one of the most common in children, and the incidence is increasing in Australia.

Now, Korean scientists have created a skin patch to measure glucose in sweat, and published the results in March 2016 in Nature Nanotechnology. They demonstrate that glucose concentrations in sweat closely followed changes in blood glucose. When the skin patch senses elevated glucose levels (or hyperglycemia), the microneedles embedded in the patch then deliver a glucose-lowering drug – metformin – under the skin.

The patch contains an array of sensors also detecting humidity, pH and temperature – parameters used to calibrate the glucose reading in sweat. When hyperglycemia is detected, a built-in heater dissolves the protective coating on the microneedles to infuse metformin.

Biomedical engineers in the USA described a similar device last year called Smart Insulin Patch. In this skin patch, the insulin-loaded microneedles themselves are sensitive to hyperglycemia, which triggers their dissolution, delivering insulin into the body when needed.

Glucose monitoring and management

The GlucoWatch was the first non-invasive real-time glucometer on the market, over a decade ago. “The technology was brilliant. The new skin patch sensors are more sophisticated versions of this,” says Professor Justin Gooding, co-director of the Australia Centre for Nanomedicine at UNSW Australia, and Editor-in-Chief of the journal, ACS Sensors.

The problem with continuous glucose monitors, which are implanted under the skin, is that they can’t be worn for more than a week or two before they need to be replaced, says Gooding.

Other continuous monitors available measure glucose via a fine needle under the skin, and have been reported to irritate the skin with prolonged wear. Non-invasive sweat sensors could eliminate this problem.

Wearable devices that monitor and manage blood glucose levels automatically, build on ideas for an artificial pancreas (also called closed-loop system) from the 80’s, says Gooding. This is a network of devices that together mimic the function of a healthy pancreas.

Gooding explains that it’s challenging to create a skin patch device that can deliver different doses of insulin at different times, like an insulin pump can. Most systems deliver a constant dose, or they just dump.

“Closing the loop is the Holy Grail for diabetes management,” says , a clinical endocrinologist at Prince of Wales Hospital, Randwick and researcher at the Centre for Diabetes, Obesity and Endocrinology, Westmead.

“It’s still a bit of an art to work out how much insulin someone needs,” she says. The biggest hurdle to closing the loop is the right algorithm to calculate the correct dose of insulin to be injected at the right time.

The skin patch devices could be useful to maintain steady blood sugars between meals, but a large dose of insulin still needs to be injected for glucose spikes after a meal, says Lau. “Often you need to anticipate the spike and inject before a meal to effectively control blood sugars”, she explains.

Clinical trials of an artificial pancreas using existing constant glucose monitors and insulin pumps teamed with new advanced algorithms – to calculate insulin doses – have been scheduled to begin in 2016 by the creators from Harvard University and University of Virginia, USA.

Advances in different research areas take us closer to the possibility of a minimally invasive artificial pancreas that can be worn as a skin patch.

“Research into closed-loop systems is really important because they help us understand how technology can be used to control diabetes,” says Lau.

– Sue Min Liu