Microelectronic Devices Based on Nanomaterial-Carrier Cells - Cell Surface Engineering: Fabrication of Functional Nanoshells - page 129

This leads to the possibility of observing mechanical modulations in the cell
using graphene sheets. 1 The other advantage offered by the large area and
mechanical flexibility of the sheets is that cells can be wrapped in them
forming a bio-inorganic hybrid. 14

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7.2 Device Configurations

7.2.1 IN and OUT Devices
The difference between an interface that couples to the exterior of the cells
such as its plasma membrane from one that couples to the cell's interior are
directly linked to cell dynamics. The exterior of the cell plays a dynamic role
in its interaction with the surrounding. The cell's response is expressed in
variables such as cell-membrane potential, dynamic modulation of its ion
channels and its shape and size. The response of the cell as expressed on its
external surface features provides a diverse array of signals that can be used
to monitor the cell dynamics. The internal coupling in principle will have
access to an array of internal cellular processes and hence an even more
complex set of cell dynamics. The internal chemical potential of the cell,
changes associated with expression of internal ion channels and pumps and
dynamics of genetic expression are some of the cell dynamics that can be
possibly linked to internal coupling devices. The Out devices can interface
with the whole exterior surface area of the cell and hence can use larger-scale
nanomaterials such as graphene, transistors made of CNT networks and
semiconducting organic polymers for making the device. 5,7-9,15,16 In con-
trast, typically the requirement for internal coupling in the In devices leads
to the use of single 1D nanowires and CNTs, where the nanomaterial
penetrates the cells membrane, accessing the cells interior with minimally
invasive effects. Recent examples have demonstrated in concept the In de-
vices with internal coupling to the cells and dynamic recording of the cells
response to a controlled external stimuli. 10,17 Using such internal coupling
to target specific cell organelles such as mitochondria or the nucleus offers
significant possibilities for the application of these internal cell devices. To
achieve this, the 1D structure used to probe the interior of the cell will have
to be further reduced to the scales of cell organelles. Targeting agents that
lead to coupling with only specific cell machinery will also have to be used to
achieve this aim.
The common challenge associated with both the techniques is the
ability to relate the observed electrical signal to a specific cellular process
(or processes). This is especially challenging in the case of placing the cell
in an uncontrolled environment where multiple stimuli act on the cell and
its response is also multifaceted. Developing an electrical interface that
targets signal from only a specific cellular response-stimuli combination
can provide devices that play a specific role in study and detection of cell
dynamics. The challenge here is to make the interfacing with the cell
specific.

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