Posted by Stephanie on November 17, 1999 at 07:50:23:
Medical Tribune News Service
Imagine wearing a device on your wrist that can continuously check your blood glucose level and tell you if it is too high or too low without taking a blood sample.
Too high tech? What about a sensor implanted under your skin that can not only measure glucose levels, but can also deliver insulin from an internal insulin reservoir?
According to researchers in England, these instruments will be part of the future of diabetes treatment.
For years, scientists have been trying to develop a continuous blood glucose monitoring device, mainly for people with type 1 or insulin-dependent diabetes. Diabetes patients currently check their own blood glucose levels by taking a small blood sample, usually through a finger prick. However, complications from hypoglycemia (low blood glucose levels) can occur without warning, especially at night.
Past studies have shown that a fall in glucose levels in the tissues can predict a drop in blood glucose levels. The researchers contend that if an in-body sensor can detect a glucose drop in the tissues, hypoglycemia can be treated quickly or even avoided.
Scientists are also exploring the possibility of creating a completely non-invasive monitoring system one that can, for example, measure glucose levels by using certain wavelengths of light. These innovations were examined in an article published in the November 13 issue of the British Medical Journal.
The glucose sensors most often studied are called amperometric enzyme electrodes. An enzyme (glucose oxidase) is fixed to one end of a wire. The wire is then implanted under the skin. Glucose levels are then monitored based on reactions with the enzyme.
"These sensors work quite well outside the body, but are very difficult to make stable inside the body," said Dr. John Pickup, reader in chemical pathology at Guy's, King's College and St. Thomas's School of Medicine in London, and one of the authors of the article.
Pickup said that the technique is accurate when measuring the glucose level in a blood sample, but unknown factors have caused the electrode to get two different readings when simultaneously used inside the body and on a sample of blood. "We've struggled for a long while with implantable glucose sensors," he said.
Pickup and his colleagues have been researching glucose sensors for about 20 years.
"At the moment, fluorescence looks extremely interesting," Pickup remarked. The principle behind this technique is that certain fluorescent molecules bind to specific parts of glucose molecules. The degree of fluorescence changes when glucose is bound. Measurements can then be made by probes inserted under the skin. Pickup noted that the technique is very sensitive and less frequently subjected to some sources of interference, such as light scattering, which can disrupt a method called near infrared spectroscopy.
According to Pickup, near infrared spectroscopy is the most studied non-invasive technique. Tissues are transparent to light in a certain region of the light spectrum. Using light in this region, glucose levels can then be measured without puncturing the skin. Pickup conceded that more research needs to be done in order to perfect the technique, but "the ultimate goal is to have something completely non-invasive."
"In the future, we're going to have several different ways of measuring glucose continuously or non-invasively," Pickup said. "I doubt very much whether a single one will come to the forefront."
Pickup noted that a lot of research still has to be done before any of these techniques can be used. "The next step is to advance the concepts toward something that can be tried in patients," he said. "There's a long way to go."
SOURCE: British Medical Journal (1999;319:1289)
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