One in twelve children are born prematurely in Switzerland. If hypoglycemia develops in these premature babies and persists for over an hour, it can affect brain development. In order to prevent this, the babies’ blood sugar levels need to be measured at regular intervals, which, until now, inevitably meant taking blood samples. Drawing blood regularly from the sensitive little ones for hours on end, however, is impossible as the blood loss and stress would be too great. In a project funded by the Swiss National Science Foundation (SNSF), Empa and the University Hospital Zurich thus teamed up to develop the sensor “Glucolight”, which gages the blood sugar level through the skin, without taking any blood.
Although skin sensors already exist, they have to be calibrated before use, which means that the skin’s permeability value needs to be known. In order to establish this, the blood sugar value has to be determined via a blood sample and the glucose concentration on the skin measured. Based on these readings, the permeability can then be calculated and the sensor calibrated.
A different method to previous sensors
Glucolight spares the premature babies blood samples and enables the blood sugar level to be monitored permanently thanks to the sensor’s novel measuring technology, which comprises several parts: A microdialysis measuring head, which was developed at the University Hospital Zurich, with a “smart” membrane developed at Empa; light sources; a pump; and a microfluidics chip with a fluorometer, also developed at the University Hospital Zurich.
The smart Empa membrane contains special dye molecules, known as spiropyrans. If UV light is beamed onto these spiropyran molecules, they alter their chemical structure and become charged (polar). When irradiated with visible light, they revert to their original, neutral structure. As a result, the membrane “opens” if irradiated with UV light and glucose molecules diffuse relatively easily through the membrane from the skin. If irradiated with visible light, considerably fewer glucose molecules pass through the membrane.
Glucolight’s measuring head with the smart membrane.
Photo credit: Empa