Fluorometer Measures Glucose Levels Noninvasively

A new light-based diagnostic tool allows physicians to monitor blood sugar levels in patients who can’t give blood samples.

The Glucolight system is intended to help prevent hypoglycemia in babies born prematurely. It was developed by researchers at the Swiss Federal Laboratories for Materials Science and Technology (EMPA) and University Hospital Zurich.

Hypoglycemia can lead to brain damage in infants if it persists for more than an hour. But monitoring the condition through repeated blood samples is impossible because the blood loss and stress would be too great for an infant to bear.

Glucolight’s measuring head with smart membrane. Courtesy of EMPA.

Glucolight does not require blood samples even for calibration. Instead, it absorbs glucose through the skin and compares two fluorescence measurements to determine blood sugar concentration.

The device features a microdialysis measuring head, which was developed at University Hospital Zurich, and a smart membrane developed at EMPA. It also incorporates light sources, a pump and a microfluidics chip with a fluorometer, also developed at the University Hospital Zurich.

The smart membrane contains dye molecules known as spiropyrans, which become charged under UV light and return to a neutral state under visible light. As a result, the membrane opens when irradiated with UV light, allowing glucose molecules to diffuse through it from the skin. If irradiated with visible light, considerably fewer glucose molecules pass through the membrane.

A measurement is taken first under visible light. The small amount of glucose that passes through the membrane is mixed with reactive enzymes and pumped through the microfluidics chip, where it is measured by the fluorometer.

The process is then repeated with UV light. A computer compares the two readings.

Clinical studies using the device are expected to begin this year at University Hospital Zurich. The researchers have filed a patent application and have begun negotiations concerning large-scale production of the sensor.

Development funding came from the Swiss National Science Foundation.

For more information, visit www.empa.ch.