Implanted Wireless Glucose Sensor That Could Transform Management Of Diabetes Passes Crucial Test

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Main Category: Diabetes
Also Included In: Medical Devices / Diagnostics
Article Date: 29 Jul 2010 - 2:00 PDT

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American bioengineers have demonstrated that an implanted glucose sensor with potential to transform the management of diabetes has passed a crucial test: the device they developed worked continuously in animals for over a year, without showing signs of "tissue encapsulation" seen in trials with other similar devices.

You can read how researchers and developers from the Department of Bioengineering at the University of California San Diego (UCSD), and GlySens Incorporated, also based in San Diego, California, showed how an implantable sensor, "capable of long-term monitoring of tissue glucose concentrations by wireless telemetry", ran successfully in two pigs for a total of 222 and 520 days respectively, in a paper published online in the journal Science Translational Medicine on 28 July.

One of the challenges of developing an effective glucose sensor that sits in tissue just below the surface of the skin, is how to overcome the problem of "tissue encapsulation" which causes unpredictable fluctuations in the readings.

Dr David Gough, first author and bioengineering professor at UCSD told the press that the most important aspect of their paper is how they overcame this problem so their sensor remained insensitive to tissue encapsulation for over 500 days.

"That's a big step from a scientific point of view, and it's due to the sensor's unique oxygen detection scheme," said Gough.

He and his team hope that after human trials and FDA approval, their device may help people with diabetes manage their condition more effectively than methods currently in use such as finger sticking and short-term, needle-like glucose sensors that have to be replaced every three to seven days.

"If all goes well with the human clinical trials, we anticipate that in several years, this device could be purchased under prescription from a physician," said Gough.

Diabetes is a disease where the body has too much glucose in the blood, either because the pancreas does not produce enough insulin (the main characteristic of type 1 diabetes), or because the body's cells don't respond effectively to insulin, a condition called insulin resistance (the main characteristic of type 2 diabetes).

In both cases, to manage the disease, it is important to monitor levels of glucose so that patients can take the right amount of medication to control it.

The problem with many current methods, for example the so-called finger-sticking system where the patient pricks his or her finger to get some blood to test in a portable reader (usually done about four times a day), is that they do not monitor the level of glucose continuously, leaving open the risk of dangerous ups and downs of glucose levels, known as "glucose excursions". The more "glucose excursions" a patient has, the higher the risk of developing long term problems of diabetes, affecting the eyes, kidneys, heart, brain, feet, and nerves.

The device that Gough and his team developed and tested in the pigs is about 1.5 inches (3.8 cm) in diameter and about 5/8 ins thick (1.6 cm). It is implanted under the skin and continuously monitors tissue glucose and transmits the information without wires to an external receiver.

The device worked effectively, they said, because of its unique way of producing a reliable reading without being affected by the problem of tissue encapsulation.

It does this by taking in glucose and oxygen from surrounding tissue and using the enzyme glucose oxidase to catalyze a reaction where oxygen is consumed in proportion to the amount of glucose present.

Any oxygen left over is measured and compared to the baseline oxygen recorded by a reference sensor, so the difference indicates how much glucose is present.

The authors said that the effect of exercise and changes in local blood flow to the tissues are also in the main subtracted out in this differential oxygen sensing system, where the two sensors sit side by side in the same device.

The sensors used in the animal trials sent the glucose information to a data recorder the size of a cell phone.

Gough said the data could be made useful in many ways, for example it could be sent to cell phones or displayed in other ways.

"There are parents with diabetic children who spend their nights worrying that their child in a nearby bedroom may go into nocturnal hypoglycemia," he said, explaining that a continuous glucose sensor could trigger an alert if the level dropped too low in the night.

"Four finger sticks per day to measure glucose levels is the current standard of care, but blood glucose can go on significant excursions between sticks," said Gough.

In contrast, a long term implanted monitor would keep measuring glucose day and night.

"We are moving toward something that will be automatic and quite unobtrusive," said Gough.

"Others wouldn't even know if someone is using a glucose sensor. Our goal is to get people off the finger stick cycle," he added.

He said if the device passes human trials, it could be implanted in patients in a simple outpatient procedure.

"Function of an Implanted Tissue Glucose Sensor for More than 1 Year in Animals."
David A. Gough, Lucas S. Kumosa, Timothy L. Routh, Joe T. Lin, and Joseph Y. Lucisano.
Sci Transl Med Vol. 2, Issue 42, p. 42ra53, published online 28 July 2010
DOI: 10.1126/scitranslmed.3001148

Additional source: UCSD.

Written by: Catharine Paddock, PhD
Copyright: Medical News Today
Not to be reproduced without permission of Medical News Today

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