Contact lenses react to blood-sugar levels http://www.newscientist.com/article.ns?id=dn7182
Contact lenses that change their appearance according to the wearer's blood-sugar level could one day help people with diabetes keep track of their levels non-invasively, new research suggests. Diabetes affects the body's ability to make or use the hormone insulin, which can cause dangerously large swings in levels of blood sugar, or glucose. Currently, most people suffering diabetes monitor their blood sugar by pricking their skin and drawing blood. But Chris Geddes, the study's lead author and associate director of the Center for Fluorescence Spectroscopy at the University of Maryland, US, has tried to create less painful alternatives. Developing a monitoring system through contact lenses makes sense because many people with diabetes also need glasses or contact lenses due to the way diabetes affects the blood vessels in the retina, Geddes says. To make glucose-sensing contacts, scientists added boronic acid to disposable contact lenses. Moisture from the tear ducts contains glucose that binds with the molecules of boronic acid, with the reaction causing fluorescence. A handheld device flashes a blue light into the eye and measures the intensity of the resulting glow, letting the user know their blood glucose level. Early snag When they were working on the contact lens, Geddes and his group hit a snag early in the development phase. Most boronic acid molecules prefer a slightly alkaline environment. But the inside of a contact lens is slightly acidic. "We had to go back to the drawing board and design molecules that used boronic acid yet survived in a mildly acidic environment," Geddes says. "They also had to be sensitive to ultra-low concentrations of glucose." Geddes' team is looking at several options for users. Rather than having the entire contact lens glow, tiny sensor spots could be placed around the contact lens. Those spots could monitor glucose, as well as sodium, cholesterol and potassium. Another sugar - fructose - is present in tears, but it exists in much lower concentrations so Geddes says it should not interfere with the glucose readings. Time lag Glucose levels in tears lag about 30 minutes behind levels in the blood, but Geddes says the delay is not a problem. Most people with diabetes have gaps of hours in between their skin prick tests, so a contact lens approach would still be a more timely and convenient method. The group is also working on a contact lens that would change colour like a traffic light - from green to yellow to orange to red - enabling the wearer or an observer to determine a broader range of blood sugar level, from too low to too high. The system is not the first non-invasive glucose monitoring system to be developed. The US Food and Drug Administration approved another system, called GlucoWatch, in 2001. GlucoWatch, which is worn on the wrist, applies a small electrical current to the skin, drawing the fluid between cells through the skin to test it for glucose. But the company that makes GlucoWatch still recommends occasional blood sugar monitoring through finger pricks. The new contact lenses are not yet on the market. Geddes and his team are currently looking for commercial partners. Journal reference: Current Opinion in Biotechnology (vol 16, p 100) You are a subscribed member of the infowarrior list. Visit www.infowarrior.org for list information or to unsubscribe. This message may be redistributed freely in its entirety. Any and all copyrights appearing in list messages are maintained by their respective owners.
