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HIGH blood sugar levels can be detected within five minutes by a monitor
implanted under the skin. The brainchild of American researchers, the monitor
will greatly improve diabetics’ control over their sugar levels.

Jerome Schultz and his colleagues at the University of Pittsburgh in
Pennsylvania designed the monitor as a semi-permeable hollow tube, 5 millimetres
long and 0.5 millimetres in diameter. The tube is filled with tiny hollow beads
made of a permeable carbohydrate called dextrin and fluorescent proteins.

The beads are dyed to absorb blue light. Inside the beads is a form of
glucose that will attract the proteins in the absence of blood sugar. So if
there is no glucose under the skin around the tube, almost all of the proteins
are drawn inside the beads.

As a result, when blue light shines on the sensor, no fluorescence is seen.
“The beads act like an umbrella, or shield, to prevent the light from getting to
the protein, and hence prevent fluorescence,” says Schultz.

But as blood sugar levels in the body rise, glucose molecules diffuse into
the tube. The proteins come out of the beads because they are more strongly
attracted to blood sugar and bind to the glucose, so when they are illuminated
with a blue light they glow green. “The protein molecules shuttle from inside
the bead to outside the bead depending on the glucose levels,” says Schultz.

The green glow is too feeble to be seen by the naked eye, but Schultz says a
small electronic device about the size of a wristwatch could shine blue light on
the skin, measure the glow and display a digital read-out of glucose levels. The
monitor is described in a forthcoming issue of Analytical Chemistry.