Humans have adorned their bodies with tattoos for thousands of years. Be it for social or political distinctions, or merely for self-expression, this ancient art form could soon be used to monitor the blood sugar level of a person with diabetes. Many diabetics have to endure the tedious and painful process that involves pinpricks and glucose strips. So, when Heather Clark, analytical chemist for the biomedical engineering group at the Charles Stark Draper Laboratory, was challenged by a director at Draper to look into possible new methods for glucose testing, she was intrigued. “At first glance, I didn’t think that it could be done, but as I looked into it and thought about it, I saw a way to do it,” Clark said. Pictured is Heather Clark, analytical chemist in the biomedical engineering group at the Charles Stark Draper Laboratory and optical nanosensors task leader. Clark and her colleagues believe they have discovered a discreet and painless way for diabetics to monitor their blood sugar levels – with a “tattoo” of sorts. The “quasitattoo” is made of a material that consists of 120-nm polymer beads containing fluorescent dye and sensor molecules designed to detect a chemical target. Thus far, the Cambridge-based lab has successfully tested, in mice, a similar tattoo that detects sodium levels and is now looking to mimic this method for measuring glucose. The red glow from nanosensors injected into this single cell indicates the level of sodium within the cytosol. Images courtesy of Draper Laboratory. The plan is to place the polymer beads just shallow enough under the skin that they could easily be removed, making them less permanent than ink. Once injected into the skin, the sensor molecules can pull the targeted chemical, such as glucose, into the polymer from the fluid that surrounds the cells. The beads bind to specific ions, and the number of ions present determines the intensity of the fluorescence, measuring the ion flux in a single cell. The brighter the fluorescence, the greater the concentration of the chemical target – in this case, glucose.Diabetic patients embedded with the quasitattoo would then use a kind of infrared device to painlessly scan the tattoo to read their blood sugar status.“It’s unique because it doesn’t have any enzymatic components to be used up,” Clark explained. Blood glucose test strips continually need to be replaced. “Other monitors, even nanosensors, have a limited lifetime, which makes implanting them difficult.”According to Clark, it is hard to predict when the sensor will be ready for use in humans, but she expects animal testing to begin within the month. “I have been surprised by the overwhelmingly positive response we have gotten from diabetic patients,” she added. “Even though we are at such an early stage, it seems to have generated a lot of enthusiasm.”