Information Technology Reference
In-Depth Information
transport that interacts with the functioning of cellular processes other than
gene regulation (e.g., ionic transport); and (2) information transport through
the manipulation of gene expression.
Electronic/Ionic Communication
Direct electronic communication with ionic transport in neurons has been
demonstrated [40]. Signals were supplied to neurons through a capacitor struc-
ture composed of a p-doped silicon electrode with a thin-film oxide between
the electrode and the cell. A voltage pulse applied to the silicon electrode
elicited an action potential in the neuron. The simplest type of stimulation was
a positive voltage step applied to the doped silicon, inducing a negative charge
at the portion of the cellular membrane in contact with the silicon capacitor
and a positive charge on the portion of the membrane most distant from the
capacitor. The intracellular response was an exponentially decaying voltage
step [98]. With properly designed structures, this intracellular voltage pulse
had a sufficient amplitude and duration to trigger an action potential [98].
Silicon structures have been constructed that both stimulate and record the
action potential from an individual neuron [98]. The same investigators have
constructed a device that transported a signal from the silicon substrate into
an action potential, which elicited an action potential in a neighboring neuron
that was subsequently recorded by a transistor on the silicon substrate [124].
This was a significant advance as this structure demonstrated all three major
communication pathways in a single hybrid device.
Information Transport into Genetic Regulatory Circuits
ELECTRICALLY INDUCIBLE PROMOTERS While chemical means may be used
to communicate with genetic regulatory circuits, physical mechanisms would
be advantageous for whole-cell systems interfaced to physical systems. Optical
excitation may be used to regulate both bacterial and eukaryotic photosynthesis
genes or constructs hosting their light-responsive promoters. However, gene ex-
pression control with current or voltage would be more easily realized in hybrid
whole-cell/microelectronic devices. A recent review summarizes the effects of
electromagnetic fields (EMFs) and electric current pulses in living cells, includ-
ing effects on gene expression [59]. Interestingly, while many of the most well-
defined biological EMF effects have come from gene expression studies, much
of this body of work has been difficult to reproduce. The most extensive series
of investigations that implicate EMF effects on gene expression have been from
the studies of Goodman and Henderson [45]. This group has published reports
of
MYC
,
-actin, and histone H2B induction levels of up to threefold in HL60
cells after a 20-min exposure to several types of EMF signals [45]. However,
rigorous attempts to repeat these experiments in independent laboratories have
failed. Other researchers using nuclear run-on assays in T lymphoblastoid cells
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