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| Home > Publications database > Using flicker noise in Graphene Field-Effect Transistors for biosensing |
| Contribution to a conference proceedings | FZJ-2026-04927 |
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2026
Abstract: Graphene-based field-effect transistors (GFETs) functionalized with lipid monolayers provide a controlled and label-free platform for studying membrane-associated proteins [1]. We have recently shown that the flicker noise of the device changes upon protein binding even when the charge-neutrality point remains at the same gate voltage [2]. Our system consists of GFETs with a protein (Ypt7) embedded in a lipid monolayer. The Ypt7-protein is used to bind a larger protein complex (HOPS) involved in membrane fusion processes. The Ypt7 with its binding-pocket extends to 3.8nm above the membrane, and binding events with HOPS take place beyond the Debye screening length in physiological buffer. Consistently, these do not appear in a shift of the charge neutrality point. However, the Ypt7 is highly mobile due to its hypervariable domain (HVD). Since HOPS binding leads to a reduction in noise as well as to stretching of the HVD, we believe that the change in noise relates to the motion of the HVD. We distinguish between two main transduction mechanisms that lead to a change in the noise amplitude: A direct mechanism where fluctuations of the charged binding-pocket result in an AC-coupling to the channel, or an indirect mechanism where the motion of the HVD affects the lipid interface at the conduction channel. Here, we present experiments and first results that lead toward understanding of the microscopic origin of the changes in the flicker noise in liquid gated graphene devices. Besides information on how passivation and lipid monolayer formation affect the device performance, we present the influence of the ionic strength of the buffer on the noise as well as negative controls. Furthermore, we investigate the influence of the anchoring of the Ypt7 to the lipid monolayer. This leads to a better understanding of how fluctuations of anchor groups might be exploited to investigate different types of large proteins using noise to circumvent the limitations set by the Debye length.
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