Grégoire Bastide, Anna Remund, Dina Oosthuizen, Nina Derron, Philipp Gerberb and Ines Weber

We developed a graphene-based field-effect transistor (gFET) capable of sensing and quantifying the presence of glucose, even in urine samples. To achieve this, we established a modification procedure for the graphene channel through the electrosynthesis of an electroactive polymer, onto which we integrated the glucose oxidase enzyme.

Furthermore, we demonstrated that the device response in the presence of glucose is attributed to the pH decrease in the vicinity of the graphene channel, resulting from the enzyme-catalyzed degradation of glucose. As a result, we can monitor changes in the degree of protonation of the electroactive polymer by assessing alterations in the conductivity properties of the gFET.

Thus, we leveraged the excellent electrical properties of graphene to use it as a conductive substrate onto which controlled polymer growth is achievable through electrochemical synthesis. Additionally, by employing a polyaniline with appended amino groups, we achieved a material with significant sensitivity to pH variations, enabling the conversion of enzymatic activity into an electronic readout.

The biosensors exhibit remarkable attributes, including a low limit of detection (LOD) of 4.1 μM. They also display a glucose detection range spanning from 10 to 1000 μM under flow conditions and a response time of 190 seconds. Moreover, they operate effectively under low gate-source and drain-source voltages. As previously mentioned, these biosensors can monitor glucose levels in urine samples, showcasing their potential for developing point-of-care glucose testing devices.

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