  Graphene, the atomically-thin honeycomb carbon lattice, is a highly
conducting 2D material whose exposed electronic structure offers an ideal
platform for sensing. Its biocompatible, flexible, and chemically inert nature
associated to the lack of dangling bonds, offers novel perspectives for direct
interfacing with bioelements. When combined with its exceptional electronic and
optical properties, graphene becomes a very promising material for
bioelectronics. Among the successful bio-integrations of graphene, the
detection of ionic currents through artificial membrane channels and
extracellular action potentials in electrogenic cells have paved the road for
the high spatial resolution and wide-field imaging of neuronal activity.
However, various issues including the low signals amplitude, confinement and
stochasticity of neuronal signals associated to the complex architecture and
interconnectivity of neural networks should be still overcome. Recently, grain
boundaries found in CVD graphene were shown to drastically increase the
sensitivity of graphene transistors providing nanoscale sensing sites. Here we
demonstrate the ability of liquid-gated graphene field effect transistors
(G-FET) on which hippocampal neurons are grown for real-time detection of
single ion channels activity. Dependence upon drugs and reference potential
gating is presented and is found compatible with the nanoscale coupling of a
few ion channels to graphene grain boundaries.
