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Jun 11, 2004

A sensor that glows at varying intensities depending on blood sugar concentrations can perform under conditions similar to those in the body GluCath inserted into a blood vessel and gives a continuous blood glucose reading. It uses an optical sensing device.

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New Concept In Non Invasive Blood Glucose Monitoring


The GluCath catheter is inserted into a blood vessel and gives a continuous reading.

University of California researchers in Santa Cruz, Calif., have developed a novel optical glucose sensor to test sugar levels in diabetics.

To monitor the blood sugar of diabetics means drawing blood several times a day, usually from finger pricks, but glucose levels can fluctuate widely throughout the day, Bakthan Singaram, a professor of chemistry and biochemistry at UCSC, said in a statement tuesday.

The application of the technology closest to yielding a marketable product is a catheter device, called GluCath, for monitoring blood glucose levels in hospitalized patients.

Glucose levels must be regularly monitored in patients in intensive care units and others fed intravenously with glucose drips, but that requires frequent blood samples, which is painful for the patient and expensive.

"The GluCath catheter is inserted into a blood vessel and gives a continuous reading, and it can sound an alarm if the glucose level goes too high or too low," said Todd Wipke, of UCSC, but a member of Singram’s research team.

We are very excited about the prospects for our optical glucose sensor to be used in a viable device for continuous glucose monitoring," Singaram said.

The optical glucose sensor consists of a fluorescent chemical complex immobilized in a "thin-film hydrogel." The hydrogel, a biocompatible polymer similar to that used to make soft contact lenses, is permeable to glucose. The sensing system has two components: a fluorescent dye and a "quencher" that is responsive to glucose.

In the absence of glucose, the quencher binds to the dye and prevents fluorescence, while the interaction of glucose with the quencher leads to dissociation of the complex and an increase in fluorescence.

Singaram’s team tested the sensor by mounting it in a flow cell and circulating a solution with varying concentrations of glucose through the cell. The results showed that the system functions as a continuous glucose monitor capable of operating under physiological conditions. The sensor shows outstanding glucose response over the full range of glucose levels that might occur in a diabetic, Singaram said.

"This is the first system to show reversible optical sensing of glucose with a thin-film hydrogel. We tested the sensor under conditions that are as close as possible to the physiological conditions under which a continuous glucose monitor would have to operate," he said.

The researchers have also applied the hydrogel to the end of an optical fiber, enabling the signal from the glucose sensor to be transmitted through the optical fiber.

A device that can provide continuous monitoring of blood glucose levels has been eagerly sought by many research groups for more than a decade, with limited success. Singaram started working to develop a glucose sensor at the suggestion of Paul Levin, founder of Palco Labs, a Santa Cruz company that makes products for diabetics. Palco funded the first two years of research on the optical glucose sensor, but was eventually unable to continue its support.

"The support from Palco Labs carried us through the early stages when we were stumbling around and trying to figure out how to do this," Wessling said. Singaram’s group is now collaborating with a local company, Glumetrics LLC, which is developing a line of products based on the optical glucose sensor. The findings were published in the international journal Angewandte Chemie.


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