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Wednesday, March 04, 2015

High-tech ink could detect blood glucose


Researchers filled ordinary ball pens with special bio-inks that react with several chemicals including glucose. By simply drawing on the skin the ink can accurately detect blood glucose levels
A new simple tool developed by nanoengineers at the University of Cali fornia, San Diego, is opening the door to an era when anyone will be able to build sensors, anywhere, including physicians in the clinic, patients in their home and soldiers in the field. The team from the University of California, San Diego, developed high-tech bio-inks that react with several chemicals, including glucose. They filled off-the-shelf ballpoint pens with the inks and were able to draw sensors to measure glucose directly on the skin and sensors to measure pollution on leaves.Skin and leaves aren't the only media on which the pens could be used. Researchers envision sensors drawn directly on smart phones for personalised and inexpensive health monitoring or on external building walls for monitoring of toxic gas pollutants. The sensors also could be used on the battlefield to detect explosives and nerve agents. The team, led by Joseph Wang published their findings in Advanced Healthcare Materials.
“Our new biocatalytic pen technology, based on novel enzymatic inks, holds considerable promise for a broad range of applications on site and in the field,“ Wang said.
The biggest challenge they faced was making inks from chemicals and biochemicals that aren't harmful to humans or plants; could function as the sensors' electrodes; and retain their properties over long periods in storage and in various conditions. Researchers turned to biocompatible polyethylene glycol, which is used in several drug delivery applications, as a binder.
To make the inks conductive to electric current they used graphite powder. They also added chitosan, an antibacterial agent which is used in bandages to reduce bleeding, to make sure the ink adhered to any surfaces it was used on. The inks' recipe also includes xylitol, a sugar substitute, which helps stabilise enzymes that react with several chemicals the do-it-yourself sensors are designed to monitor.
REUSABLE GLUCOSE SENSORS
Wang's team has been investigating how to make glucose testing for diabetics easier for several years. The same team of engineers recently developed non-invasive glucose sensors in the form of temporary tattoos. In this study, they used pens, loaded with an ink that reacts to glucose, to draw reusable glucose-measuring sensors on a pattern printed on a transparent, flexible material which includes an electrode.Researchers then pricked a subject's finger and put the blood sample on the sensor.
The enzymatic ink reacted with glucose and the electrode recorded the measurement, which was transmitted to a glucose-measuring device. Researchers then wiped the pattern clean and drew on it again to take another measurement after the subject had eaten.
Researchers estimate that one pen contains enough ink to draw the equivalent of 500 highfidelity glucose sensor strips. Nanoengineers also demonstrated that the sensors could be drawn directly on the skin and that they could communicate with a Bluetooth-enabled device to gather data.
SENSORS FOR POLLUTION
The pens would also allow users to draw sensors that detect pollutants and potentially harmful chemicals sensors on the spot. Researchers demonstrated that this was possible by drawing a sensor on a leaf with an ink loaded with enzymes that react with phenol, an industrial chemical, which can also be found in cosmetics, including sunscreen. The leaf was then dipped in a solution of water and phenol and the sensor was connected to a pollution detector. The sensors could be modified to react with many pollutants, including heavy metals or pesticides