Talented Tattoos

Monitoring glucose levels is a bit of a pain for doctors and patients – finger prick tests remain the standard for self-monitoring in diabetes, but they’re uncomfortable and invasive; sometimes causing compliance problems. A research team from the University of California, USA, may have found a solution in a temporary, stick-on tattoo.

The tattoo contains carefully positioned electrodes, and when a charge is applied, sodium ions in the interstitial fluid carrying glucose molecules migrate to the electrodes, allowing the built-in sensor to measure the strength of the electrical charge produced by the glucose (1). Sounds like it could be a hit with patients if it makes it to market.

Noninvasive monitoring is a popular research goal though, and the University of California team have plenty of competition: Google is working on an ambitious project to measure the glucose in tears using their “smart contact lens” (2), while a team at Princeton University, NJ, USA, recently published research on a laser that reads glucose levels when it’s pointed at your palm (3).

As for electrochemical techniques, the tattoo sensor is far from the first attempt – in 2002, the US Food and Drug Administration approved GlucoWatch, a device worn on the wrist which used an electrical current to detect glucose levels and provide readings. However, the technology had problems. Users found it uncomfortable or even painful to wear, and some experienced skin irritation caused by the electric current. It also required a two-hour warm up period, and had to be calibrated with a finger prick test. Far from ideal.

So what makes the tattoo sensor different? It uses a lower current density, and a layer of agarose gel covers the electrodes to minimize skin irritation. Made of temporary tattoo paper, the sensor is low-cost and easily disposed of after use, and it can detect glucose at micromolar levels, even in the presence of other substances. Although it can’t yet display a direct numerical measurement to the user (it must be removed and analyzed), the creators are hopeful this will be the next step. “Our eventual aim is to create a device with bluetooth capabilities, which will send this information directly to the patients’ doctor in real-time, or store data in the cloud,” says study author Amay Bandodkar.

Diabetes monitoring isn’t their only aim – other potential uses include alcohol or drugs monitoring, biomonitoring of other chemical markers, or possibly even transcutaneous drug delivery.

With many approaches being taken to non-invasively monitor diabetes, it’s likely to be only a matter of time before the finger prick test is a thing of the past – but it remains to be seen which alternative will come out on top.