Transcript (7)_nanowire_neuron2_Parra

Erika A. Parra
EE235
4/9/07
 Neuron
Terminology
 NW-FET & Neurons
 Device Fabrication
 Results
• Signal Propagation
• Signal Blocking
• Multi-Neurite Structures
 Conclusions
 Soma
– 3 to 18 um
 Dendrites – cellular
extensions, <1um
thick
 Axon – cable-like
projection, can be
>1m, also <1um thick
 Axon terminal
 IC = intracellular
1. Resting State ~ -70mV
Na++
Cell Action Potential
K+
2. Depolarization
Na+
+
++
3. Repolarization
++
+
• Potential outside of cell (by NW)
becomes more negative (mirror
image)
• Accumulation of carriers at NW
• P-type NW conductance enhanced
1. SiNW (20um) growth via
CVD with Au cluster
2. Diborane (B2H6) CVD for
doping (p-type)
3. Alignment through flowdirected technique
4. Patterned and deposited
contacts for source and
drain (Ni). Passivated
contacts (Si3N4) to survive
cell culture conditions
5. Patterned 50um squares
for cell body and 3um
wide lines for axion and
dendrite grown.
Deposited polylysine for
adhesion of and directed
growth
6. Cell culturing
NW-Neuron Array
NW Element
Yield - 90%
Optical
Soma stimulation
Simultaneous axon and dendrite peak
spreading measurement- new
Superimposed signals:
• Peak reduction & temporal spreading in
dendrite
• Measured latency matches previously
reported values
NW3 Stimulated
Peak amplitude decrease at 0.4V
Back propagation signal to soma
unaffected by increasing potential
Axon end signal blocking at 0.9V
-Suggests action is localized
Propagation speed comparable in
both directions through axon
Intracellular
NW-Axon
axon
Soma
Spike propagation
w/o IC electrode
15ms 0.5nA
NW4 not connected
Biphasic stimuli
500us train width




Signal mapping tool with high spatial and temporal
resolution (150 devices with 400nm interspacing)
Inhibits or stops signal propagation while mapping
signal flow to dendrites and axons
Reproducibility of NW-cell devices for flexible real-time
cellular assays for drug discovery and testing – 43 out
of 50 working devices over 500um axon
Possible interface for implanted devices
 Micropipette
electrodes
• Intracellular and extracellular
• Resolution of 100nm per pipette and 10um
between pipettes
• Difficult to multiplex
 FET
arrays
• 10um and larger on edge and 10um between
electrodes
• Size limits neuron analysis – cannot look at
individual axons or dendrites
Soma initiated
NW-Axon initiated
500ms step of 0.1nA
Temporal correlation
Applied biphasic potential
1) 0.5V (successful 86%)
2) 0.3V (below threshold)
3) 0.5V after TTX (toxin that
blocks action potentials)