With this nano-sized biosensor, diabetes patients can measure their glucose levels with the fluid from the tears of their eyes. Image: Fraunhofer IMS |
Sticking
yourself in the finger day after day: For many diabetics, this means of
checking blood glucose is an everyday part of life. Especially for
patients with Type-1 diabetes, who always have to keep a close eye on
their levels, since their bodies are incapable of producing the insulin
to break down the glucose in the blood. Several times a day, they have
to place a tiny drop of blood on a test strip. It is the only way they
can ascertain the blood glucose value, so they can inject the correct
amount of insulin needed. And this pricking is not only a burdensome: it
may also cause inflammation or cornification of the skin. And for
pain-sensitive patients, the procedure is agony.
The
daily sticking of the finger may soon become a thing of the past,
thanks to a diagnostic system with Fraunhofer technology built-in. The
underlying concept is a biosensor that is located on the patient’s body.
It is also able to measure glucose levels continuously using tissue
fluids other than blood, such as in sweat or tears. The patient could
dispense with the constant needle pricks. In the past, such bioelectric
sensors were too big, too imprecise and consumed too much power.
Researchers at the Fraunhofer Institute for Microelectronic Circuits and
Systems IMS in Duisburg have recently achieved a major breakthrough:
They have developed a biosensor in nano-form that circumvents these
hurdles.
Diagnostic system in miniature
The
principle of measurement involves an electrochemical reaction that is
activated with the aid of an enzyme. Glucose oxidase converts glucose
into hydrogen peroxide (H2O2) and other chemicals whose concentration
can be measured with a potentiostat. This measurement is used for
calculating the glucose level. The special feature of this biosensor:
the chip, measuring just 0.5 x 2.0 mm, can fit more than just
the nanopotentiostat itself. Indeed, Fraunhofer researchers have
attached the entire diagnostic system to it. “It even has an integrated
analog digital converter that converts the electrochemical signals into
digital data,” explains Tom Zimmermann, business unit manager at IMS.
The biosensor transmits the data via a wireless interface, for example
to a mobile receiver. Thus, the patient can keep a steady eye on his or
her glucose level. “In the past, you used to need a circuit board the
size of a half-sheet of paper,” says Zimmermann. “And you also had to
have a driver. But even these things are no longer necessary with our
new sensor.”
Durable biosensor
The
minimal size is not the only thing that provides a substantial
advantage over previous biosensors of this type. In addition, the sensor
consumes substantially less power. Earlier systems required about 500
microamperes at five volts; now, it is less than 100 microamperes. That
increases the durability of the system – allowing the patient to wear
the sensor for weeks, or even months. The use of a passive system makes
this durability possible. The sensor is able to send and receive data
packages, but it can also be supplied with power through radio
frequency.
The
glucose sensor was engineered by the researchers at Noviosens, a Dutch
medical technology firm. Since it can be manufactured so
cost-effectively, it is best suited for mass production. These
non-invasive measuring devices for monitoring blood glucose levels may
become the basis for a particularly useful further development in the
future: The biochip could control an implanted miniature pump that,
based on the glucose value measured, indicates the precise amount of
insulin to administer. That way, diabetes patients could say goodbye to
incessant needle-pricks forever.
Source: Fraunhofer Institute