Scientists at the ETH Zurich's Department
of Biosystems Science and Engineering (D-BSSE) in Basel have developed a new
implantable device that can monitor acid build-up in patients with diabetes as
well as produce insulin.
Insulin is a natural hormone produced by
the beta cells in the pancreas. It allows the body to use sugar (glucose) from
carbohydrates in the food for energy or to store glucose for future use.
Insulin regulates blood sugar levels from getting too high (hyperglycemia) or
too low (hypoglycemia). For humans, the normal blood pH value is between 7.35
Patients with type 1 diabetes in
particular are at risk of high acid levels. Because their bodies do not produce
insulin, their cells are unable to absorb any glucose from the blood and have
to tap into another energy source: fat reserves. These patients are also in
danger of death due to ketoacidosis which is a metabolic shock resulting from
an excess of beta-hydroxybutyrate, an acid which supplies the muscles and brain
with energy through the bloodstream.
The new implantable molecular device that
has been developed by Bioengineers at the ETH Zurich's Department of Biosystems
Science and Engineering (D-BSSE) consists of two modules: a sensor that
constantly measures blood pH and a gene feedback mechanism that produces the
necessary amount of insulin.
Both these modules were constructed from
different biological components, such as proteins and genes that had been
incorporated into cultivated renal cells. Scientists then embedded millions of
these customized cells in capsules, which can be implanted in the body.
The device is fitted with a pH sensor,
which measures the precise acidity levels in the blood. If the pH value falls
below 7.35, the sensor will send a trigger to produce insulin. A low pH
value of 7.35 is a sure sign that the person has type 1 diabetes. Blood pH can
also drop due to excessive alcohol consumption or exercise on account of the
over-acidification of the muscles, but will not fall below 7.35. Insulin
ensures that cells in the body absorb glucose again and switch from fat to
sugar as their source of energy for metabolism, as a result of which the pH
value rises again.
The implant's pH sensor automatically
turns off as soon as the blood pH value returns to the ideal range and the
reprogrammed cells stop producing insulin.
This research has been successfully tested
on mice with type 1 diabetes and related acidosis. Capsules that were implanted in the mice
produced the amount of insulin appropriate to their individual acid
measurements. These tests were comparable to that of healthy mice that
regulated their insulin levels naturally. The implant also compensated for
larger deviations in blood sugar.
Commenting on the new study, lead
researcher Martin Fussenegger says, "Applications for humans are conceivable
based on this prototype, but they are yet to be developed. We wanted to create
a prototype first to see whether molecular prostheses could even be used for
such fine adjustments to metabolic processes."
Fussenegger further added, "Preparing this
product for the market is beyond the scope of the institute's staff and
financial resources, thus requiring collaboration with an industrial partner."