Interfacing Biomolecules, Cells and Tissues with Nanowire-based Electrical Devices - Applications of Electrochemistry and Nanotechnology in Biology and Medicine - page 98

when the cell was detached. Interestingly, nanoFET probes of sim-
ilar sensitivity that were not coated with a phospholipid bilayer
exhibited only baseline fluctuations (< ±1 mV) ( Fig. 8h ), suggest-
ing that the biochemical modification is crucial for assisting access
to the intracellular region , possibly through membrane fusion.
Next, the formation of intracellular interface between the 3D
nanoFET probes and spontaneously beating cardiomyocytes was
investigated. Embryonic chicken cardiomyocytes were cultured on
PDMS substrates 44 and then positioned to place individual cells
over the phospholipid bilayer-modified vertical (T = 90 o ) nano-
probes 44,52 ( Fig. 9A ). Representative conductance versus time data
recorded from a 3D nanoFET probed in gentle contact with a beat-
ing cell showed regularly spaced spikes with a frequency of ca. 2.3
Hz consistent with beating cardiomyocyte ( Fig. 9B, I ). The peaks
have a potential change of ~3-5 mV, S/N 2, and a sub-
millisecond width ( Fig. 9C, I ) . The peak amplitude, shape and
width have characteristics of extracellular recordings made with
nanowire devices on substrates, 44 supported by optical images rec-
orded at the same time. After a relatively brief (~40 s) period of
extracellular signals, several pronounced changes in recorded sig-
nals were observed ( Figs. 9B and C , II and III ) without application
of external force to the PDMS/cell support. Specifically, the initial
extracellular signals gradually disappeared ( Figs. 9B and B , II ,
magenta stars). There was a concomitant decrease in baseline po-
tential and new peaks emerged that had an opposite sign, similar
Figure 9. Electrical recording from beating cardiomyocytes. (A) Schematics of
cellular recording from the cardiomyocyte monolayer on PDMS (left) and highlight
of extracellular (middle) and intracellular (right) nanowire/cell interfaces. The cell
membrane and nanowire lipid coatings are marked with purple lines. (B) Electrical
recording from beating cardiomyocytes: (i) extracellular recording, (ii) transition
from extracellular to intracellular recordings during cellular entrance, and (iii)
steady-state intracellular recording. Green and pink stars denote the peak positions
of intracellular and extracellular signal components, respectively. The red-dashed
boxes indicate regions selected for (C). (C) Zoom-in signals from the corresponding
red-dashed square regions in (B). Blue and orange stars designate features that are
possibly associated with inward sodium and outward potassium currents, respec-
tively. The red-dashed line is the baseline corresponding to intracellular resting
state.