Sensing glucose for diabetes monitoring with graphene
Graphene field-effect transistors (GFETs) can be excellent glucose sensors for monitoring diabetes, new research shows. Conventional methods for monitoring blood glucose, like commercial glucometers, deliver accurate results but are frequently regarded as uncomfortable. The research introduces electrolyte-gated graphene field-effect transistors as highly sensitive, non-invasive glucose sensors to satisfy this demand.
Researchers from the International Iberian Nanotechnology Laboratory produced a matrix of 32 GFETs on a 1000 micrometer square footprint and functionalized them with glucose oxidase (GOx) enzymes. The GOx serves as a glucose recognition element, allowing electrical currents to pass through the transistor only when exposed to glucose. In the presence of glucose, the graphene biosensor showed an attomolar (aM) limit of detection and a high sensitivity of 10.6 mV/decade, outperforming previously reported glucose sensors. “Our sensor’s performance opens new horizons for minimally invasive detection of medically relevant biomarkers,” added Dr. Andrea Capasso, coordinator of the study. “We’ve demonstrated it for glucose, but this technology could be extended to other critical targets in tears, saliva, or sweat – biofluids that are often difficult to analyze due to very low analyte concentrations.”
Illustration: Man using wearable glucose monitor.
The state of the art of glucose monitoring includes finger-pricking sensors, which are highly accurate but put a demand on the patient to draw their own blood at home, which may put off up to 30% of patients. Glucose monitoring from tears and saliva has also been researched, however the low glucose concentration of these bodily fluids renders such devices impractical.
The unprecedented limit of detection of the novel graphene-based sensors, of only 1 aM, opens the potential of this sensing platform for at-home monitoring from tears and saliva. The graphene sensor was tested with artificial tears and human tear samples, consistently delivering reliable performance even with these low-glucose content fluids. The sensor was also tested with fluids that contain compounds that commonly interfere with glucose detection, such as lactate and ascorbic acid, however the GOx functionalization proved to be robust against such interferences.
The fabrication of the sensors consisted of standard graphene fabrication steps that include chemical vapor deposition (CVD) growth, graphene transfer and functionalization. These are routine steps, making the process favourable for future mass production of the devices. The response of the sensors was characterized with Raman spectroscopy, X-ray photoelectron spectroscopy, and water contact angle measurements to determine the reaction to glucose molecules. The characterizations revealed that glucose induces p-type doping in the graphene, which is reflected in electrical transport signals. Electrical transport measurements and biosensing can easily be performed with the Graphenea card or cartridge, accompanied with any of our dedicated biosensing graphene chips. These products lower the entry barriers for researchers that want to obtain fast results using graphene biosensors.
