Scientists from the University of California, San Diego, have developed and tested a tiny stick-on temporary tattoo that painlessly extracts glucose and monitors its levels in the body. It works by gently drawing glucose from between cells to the surface of the skin where it can then be measured by in-built sensors. Not only is the gadget non-invasive and discreet, it’s extremely cheap—costing just a few cents—and works just as well as the dreaded finger prick tests.

Although it’s just at a proof-of-concept stage, it’s hoped that one day it could be used to replace painful daily blood sampling, and could even be adapted to test other medically important molecules or deliver medicines.

Diabetes affects hundreds of millions of people worldwide and despite many advances in both modern medicine and our understanding of the disease, it remains one of the leading causes of deaths globally. In order to effectively manage the condition and prevent its associated problems, patients must frequently monitor their blood glucose levels which involves painful blood sampling from the finger tip. For obvious reasons, many patients are reluctant to do this, resulting in poor management of the disease. The development of painless, non-invasive monitoring techniques is therefore highly desirable.

More than a decade ago, significant progress was made towards this goal with the introduction of GlucoWatch: a wristband that worked by sucking up glucose towards the surface of skin where it was detected by built-in sensors. To do this, a small electric current was applied that caused sodium ions from the fluid between skin cells—which also carry glucose—to migrate towards the device. The glucose then enters gel filled discs within the watch that contain an enzyme, glucose oxidase, which breaks down glucose into hydrogen peroxide and oxygen. The amount of hydrogen peroxide is then measured and acts as a proxy for glucose levels.

Unfortunately, this watch was discontinued because users experienced discomfort from the electrical current. But now, a new device has been designed based on the principles of GlucoWatch, and it overcomes the skin irritation problem by using a much lower electrical current to attract the sodium ions.

As described in Analytical Chemistry, the aesthetically pleasing gadget comprises tiny electrodes printed onto temporary tattoo paper, which can then be adhered to a user’s skin. Each flexible device lasts for around a day, and once again senses glucose levels using glucose oxidase. The tattoo was tested out on seven volunteers between the ages of 20 and 40 with no history of diabetes. During initial trials, none of the participants reported feeling any discomfort, although some reported tingling for a few seconds.

UCSD/Jacobs School of Engineering

To investigate whether it could successfully pick up changes in glucose levels, volunteers were given a carb rich meal consisting of a sandwich and a can of soda. Sure enough, the device was found to pick up glucose spikes just as well as traditional monitoring methods.

At this stage, the proof-of-concept tattoo can’t provide a numerical readout that would be required to monitor a diabetic’s glucose levels; however, the researchers are working towards developing a Bluetooth instrument that would be able to send this information either to the patient’s doctor or to another device.

[Via Analytical Chemistry, UCSD, Gizmodo and Science Alert]