Biomedical Engineering Reference
In-Depth Information
Indeed, studies have shown that nanostructured interfaces can
enhance neuronal adhesion and activity. 14,32 It has been demon-
strated that CNT networks or etched silica promote cellular adhe-
sion, spreading and guidance, even in the absence of conventional
adhesion factors such as polylysine. 32b,33 Neuronal stimulation
through carbon nanotubes was demonstrated for the first time in
2005, by capacitive coupling to micron-scale pads consisting of
tightly-packed carbon nanotube pillars. 34 Then, in 2006, nanotubes
were assembled into mats using a layer-by-layer technique, and
stimulation was achieved by passing lateral current pulses through
the conductive mat. 35 In a follow-up work in 2007, the same tech-
nique was used to assemble close-packed films of photoactive
HgTe nanoparticles; illumination of the film resulted in photo-
chemistry and charge-transfer that subsequently stimulated an in-
terfaced neuron. 36 Two other separate studies demonstrated that
neurons cultured on CNT mats exhibit enhanced spiking activity
(vs. those cultured on planar control surfaces), and suggest that the
conductive, nanostructured surface enhances membrane excitabil-
ity. 37
The first electronic interface between NWs and neurons was
reported by Lieber's group in 2006 in which hybrid structures con-
sisting of nanowires FET arrays and patterned neurons were as-
sembled and electrically characterized. 38 An important aspect of
this work is the surface patterning and the incorporation of cells
with respect to the NW-FET-devices with the ability to explore the
cellular activity with the nanowires positioned directly at the vicin-
ity of the cell surface. For a FET array to be used to record neu-
ronal signals, the gate dimensions should ideally be on the na-
nometer scale, and the neurons have to sit on the non-metallized
gate of the FET, affecting the source-drain current by capacitive
coupling when the neuron undergoes a membrane voltage change.
Several recent studies provided strong support that neurons grow-
ing according to pattern exhibit healthy electrophysiological prop-
erties and synaptic connections. 39 Nevertheless, this task is intri-
guing due to the difficulty of culturing cells in well defined orien-
tations over nanoscale devices while maintaining good device
characteristics.
In this work, p- and n-type Si-NWs were incorporated into
FET device array structures in well defined positions in which they
were spatially located along the axon and dendrites or at the junc-
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