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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