Unlocking the secrets that sweat contains about our bodies could come to offer all kinds of exciting ways to maintain our physical well-being. From glucose to sodium, tracking of key chemicals in this bodily fluid could make for new, non-invasive ways to keep tabs on harmful conditions. The latest effort to tap into this assortment of physiological information comes in the form of a sweat-monitoring patch that records glucose in a subject and even releases diabetes drugs into the bloodstream to keep its levels in check.

Beginning with a structure of gold-doped graphene and, squiggly, snake-shaped gold mesh, scientists at Korea's Institute for Basic Science built the sweat-sensing patch by working electrochemically active and soft functional materials into the design. Among these are sensors to monitor humidity and glucose, which are sandwiched in between a silicone water-proof film and a sweat-collecting layer.

"The patch is applied to the skin where sweat-based glucose monitoring begins on sweat generation," explains KIM Dae-Hyeong, a scientist from the institute's Center for Nanoparticle Research. "The humidity sensor monitors the increase in relative humidity (RH). It takes an average of 15 minutes for the sweat-uptake layer of the patch to collect sweat and reach a RH over 80 percent at which time glucose and pH measurements are initiated."

These measurements of sweat glucose are then used to estimate levels of glucose in the blood. In testing, where the patch was applied to two healthy males, glucose and pH levels were monitored and an analysis then found a reliable connection between the sweat glucose readings and readings from a conventional glucose test. The teams says that hooking up the patch to a wireless power supply and data transmission unit can then allow non-invasive monitoring of glucose levels in the blood stream.

This device has some similarities with other solutions we have looked at recently, including another sweat-analyzing skin patch from 2014 and a multipurpose wristband from earlier this year. But where these promising devices allow for real-time monitoring of biochemicals, this version takes things one step further with actual drug delivery.

Fitted with an array of microneedles, the patch can deliver drugs into the bloodstream when it picks up dangerously high levels of glucose. In testing, the team applied the patch to the abdomen of diabetic mice. Here the microneedles punctured the skin and released an insulin-regulating drug called Metformin, which in turn effectively suppressed the blood glucose concentrations compared to the control group.

"One can easily replace the used microneedles with new ones," says Dae-Hyeong. "Treatment with Metformin through the skin is more efficient than that through the digestive system because the drug is directly introduced into metabolic circulation through the skin. These advances using nanomaterials and devices provide new opportunities for the treatment of chronic diseases like diabetes."

The research was published in the journal Nature Nanotechnology.

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