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Doctors newspaper online, 15.10.2019
Biocompatible sensor
Blood levels could be determined in the future without needle stick: Empa researchers are developing biocompatible nanocellulose sensors on the skin.
With the 3D printer, the nanocellulose "ink" is applied to a carrier plate. Silver particles provide the electrical conductivity of the material.
© Empa
ZURICH. The idea of measuring health-relevant values in the body via the skin has already arrived in medical diagnostics, such as sensor blood glucose measurement in diabetic patients. Researchers have now produced a new sensor that is flexible on the skin surface and particularly biocompatible because it consists of nanocellulose, reports the Empa – Swiss Federal Laboratories for Materials Testing and Research
.
Nanocellulose is a cheap, renewable raw material that is obtained in the form of crystals and fibers, for example from wood. The gelatinous substance may consist of nanocrystalline cellulose and cellulose nanofibers. Further sources for the material are bacteria, algae or production residues from food production.
0.5 millimeters thick is the "biochemistry laboratory" made of nanocellulose. researcher
could use this sensor on the skin metabolic parameters such as
Measure the concentration of calcium, potassium and nitrogen-containing ammonium ions.
This not only makes nanocellulose comparatively easy and sustainable to win. The "super pudding" also makes its mechanical properties interesting, which is why new composites with nanocellulose can be developed, which could be used as surface coatings, everyday objects such as beverage bottles or in the form of transparent packaging films.
Material from natural resources
The researchers of the Empa laboratory "Cellulose & Wood Materials" in Dübendorf (Switzerland) and Dr. med. Woo Soo Kim of Burnaby's Simon Fraser University in Canada also emphasized another feature of nanocellulose: its biocompatibility. Precisely because the material is extracted from natural resources, it is particularly suitable for biomedical research.
Researchers used nanocellulose as an "ink" in the 3D printing process ( Adv Electron Mater 2018, online December 19 ) to produce biocompatible sensors capable of measuring key metabolic levels. To make the sensors electrically conductive, the ink was added with silver nanowires. The researchers determined the exact ratio of nanocellulose and silver filaments to form a three-dimensional network, the Empa Communication notes.
It turned out that cellulose nanofibers are better suited than crystalline nanocellulose to make a crosslinked matrix with the tiny silver wires. "Cellulose nanofibers are as flexible as boiled spaghetti, but with a diameter of only about 20 nanometers and a few microns in length," says Empa researcher dr. Gilberto Siqueira.
Tiny Biochemistry Laboratory
Finally, the research team succeeded in developing sensors that measure metabolic parameters such as the concentration of calcium, potassium and nitrogen-containing ammonium ions. To further analyze the readings, the electrochemical skin sensor sends its results to a computer for further data processing. Overall, the tiny biochemistry lab on the skin is only half a millimeter thick.
While the current skin sensor specifically and reliably detects ion concentrations, the researchers are already working on a new version: "In the future, we would like to replace the silver particles with another conductive material, for example based on carbon compounds," explains Siqueira. Thus, the medical nanocellulose sensor would not only be biocompatible, but also completely biodegradable. (Eb)
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