channel, which enabled electrophysiology recordings when measured as a function of

time. By exploiting a similar approach, Hess et al. fabricated graphene-FET arrays for

simultaneous multiplexed extracellular field potential recordings from electrogenic cells

from up to eight transistors [57]. Another important field of application of graphene

structures is intracellular recording, due to the fact that monitoring intracellular action

potentials is critical for in-depth electrophysiological and toxicological investigations. In

these regards, Dipalo et al. presented a microelectrode platform consisting of out-of-plane

grown three-dimensional fuzzy graphene (3DFG) that enables recording of intracellular

cardiac action potentials with high signal-to-noise ratio. The authors exploited the gen­

eration of hot carriers by ultrafast pulsed laser for opto-porating the cell membrane and

creating an intimate contact between the 3DFG electrodes and the intracellular domain

[59], enabling the detection of the effects of drugs on the action potential shape of human-

derived cardiomyocytes (Figure 4.8). Fuzzy graphene has been also employed for

stimulation, recently. Specifically, Cohen-Karni and collaborators reported a hybrid na­

nomaterial for remote, nongenetic, photothermal stimulation of 2D and 3D neural cellular

systems [60]. The authors combined one-dimensional (1D) nanowires (NWs) and 2D

graphene flakes grew out-of-plane for highly controlled photothermal stimulation at

subcellular precision without the need for genetic modification, with laser energies lower

FIGURE 4.8

(a) SEM images of the fuzzy graphene electrode. Scale bars, 5 µm (I), 1 µm (II), and 0.5 µm (III). (b) UV-vis

absorption spectrum of the 3DFG. (c) Real and imaginary parts of the dielectric constant of 3DFG. (d)

Photocurrent generated at the interface between 3DFG electrodes and PBS under excitation with ultrafast (pi­

cosecond) pulsed laser at 1064 nm at different excitation powers. (e) Capacitive and faradaic current compo­

nents of the photocurrent generated by laser excitation. Adapted with permission [ 59]. Copyright (2021)

American Association for the Advancement of Science. Distributed under a Creative Commons Attribution

License 4.0 (CC BY) https://creativecommons.org/licenses/by/4.0/.

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