Charging the Quantum Capacitance of Graphene with a Single Biological Ion Channel

Abstract

The interaction of cell and organelle membranes (lipid bilayers) with nanoelectronics can enable new technologies to sense and measure electrophysiology in qualitatively new ways. To date, a variety of sensing devices have been demonstrated to measure membrane currents through macroscopic numbers of ion channels. However, nanoelectronic based sensing of single ion channel currents has been a challenge. Here, we report graphene-based field-effect transistors combined with supported lipid bilayers as a platform for measuring, for the first time, individual ion channel activity. We show that the supported lipid bilayers uniformly coat the single layer graphene surface, acting as a biomimetic barrier that insulates (both electrically and chemically) the graphene from the electrolyte environment. Upon introduction of pore-forming membrane proteins such as alamethicin and gramicidin A, current pulses are observed through the lipid bilayers from the graphene to the electrolyte, which charge the quantum capacitance of the graphene. This approach combines nanotechnology with electrophysiology to demonstrate qualitatively new ways of measuring ion channel currents.

Sensing at the Surface of Graphene Field‐Effect Transistors

“…[147] Nevertheless, most researches on graphene biointerfaces still use graphene on rigid solid substrates at an intermediate stage mainly focusing on understanding the complicated sensing mechanisms (as the reconfiguration of the fluidic-like lipid layer has to be considered). [149,150,151] For example, a gram-negative bacteria biomimetic membrane was deposited on CVD GFETs (fabricated on a SiO 2 /Si substrate) for detecting magainin 2, an antimicrobial agent. The presence of magainin 2 disrupts and thins the lipid membrane from a thickness of ~5 nm to ~3 nm.…”

“…[151] Graphene bioelectronics for cellular sensors will be further discussed in the next Section 4.3.…”

“…Such GFETs interfaced with biomimetic membrane can even provide enough sensitivity to investigate individual ion channel activity during the insertion of a pore-forming membrane protein. [151] Graphene bioelectronics for cellular sensors will be further discussed in the next Section 4.3.…”

Capacitance of graphene in aqueous electrolytes: The effects of dielectric saturation of water and finite size of ions

“…The QC of a single-layer graphene [17] was first measured by Xia et al in an ionic liquid and in an aqueous solution of salt [18]. Some of the more recent studies of the graphene QC in aqueous solutions involve a correlated in situ electrochemical Raman spectroscopy [19], as well as charging of graphene through a biological ion channel in a lipid bilayer adjacent to graphene [20], showing the versatility and the promise of operating graphene devices in the capacitor mode. It is noteworthy that most of the above-mentioned studies of solution-gated graphene devices have achieved quite high doping densities of graphene by both electrons and holes, reaching the range of 10 13 -10 14 cm −2 .…”

Vapor‐Phase‐Gating‐Induced Ultrasensitive Ion Detection in Graphene and Single‐Walled Carbon Nanotube Networks

“…Recently, it has been shown that the conductivity of the 1D channel of an SWNT is sensitive to individual positive ions—attributed to the simultaneous drop in mobility and charge transfer . Surprisingly, although charged entities in liquid phase (electrolytes) are well known for highly efficient gating, the possibility of a vapor‐phase gating by a stream of charged particles has not yet been explored.…”