Biomedical Engineering Reference
In-Depth Information
Mitral cells
Lateral olfactory tract
Pyramidal cells
2
3
1
a
3
Pyramidal cells
c
2
Stimulation
electrode
Patch clamp
pipette
4
5
3
Pyramidal cells
I
II
III
2
Bottom view
Lateral
olfactory
tract
b
d
10 pA
10 ms
Top view
1 nS
Top view
10 ms
20 µm
FIGURE 5.48
Nanowire.FET.arrays.for.recording.from.brain.slices..(From.Quan.Qing,.Sumon.K..Pal,.
Bozhi.Tian,.Xiaojie.Duan,.Brian.P..Timko,.Tzahi.Cohen-Karni,.Venkatesh.N..Murthy,.and.Charles.M..
Lieber,.“Nanowire.transistor.arrays.for.mapping.neural.circuits.in.acute.brain.slices,”.
Proc. Natl. Acad.
Sci. U. S. A.
.107,.1882-1887,.2010..Figure.contributed.by.Venkatesh.Murthy.and.Charles.M..Lieber.)
an extracellular position
. he “magic” is that the gMμEs are derivatized with a peptide that gen-
erates phagocytosis of the gMμE, so that the neuron engulfs it and forms a low-resistance actin
ring around the stalk of the gMμE. Action potentials and subthreshold potentials were recorded
with quality and signal-to-noise ratio matching that of conventional intracellular patch clamp
pipettes for up to 2 days. It is not clear that the “mushroom” geometry is essential, or whether the
enguling peptides are the only strategy available to access the intracellular milieu: the group of
Nicholas Melosh at Stanford University has recently presented a variation of this design whereby
the post is cylindrical and the cell forms a seals with a hydrophobic 5 to 10 nm narrow band
on the post that is functionalized with butanethiol, which causes it to fuse with the cell mem-
brane (seal resistances of 3.8 ± 1.9 GΩ were recorded). In any case, these “in-cell” extracellular
electrodes, as Spira's group calls them, are expected to revolutionize the technology of neuronal
recordings both in vitro and in vivo.
5.8 Patch Clamp Chips
he patch clamp chip ield has brought many interesting lessons for both biologists and engi-
neers alike. Many biologists had predicted that, unless the surface of the chips were built with
glass to imitate that of patch clamp pipettes, the chips would never provide the same quality
of recordings—yet patch clamp recordings obtained with all-PDMS devices are now routine.
Most engineers attempted designs that incorporated glass or silicon, but aperture fabrication (or
fabrication throughput) was an immense challenge. he solutions were very creative and worth
studying; however, the ield has been somewhat outsmarted by Spira's (and others) molecular
trickery that results in much more benign “in-cell” probes (see
Figure 5.49
).
