Biomedical Engineering Reference
In-Depth Information
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Figure 3.13
Schematic representation of valve barriers for reversible separation of
microfluidic chambers A) pressure reduction opens the valve opening a
microfluidic connection channel between the cell culture chambers
B) Pressure build-up by filling the pressure chamber closes the valves,
separating the cell culture compartments.
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(Reprinted by kind permission of Elsevier BV.)
fabricated soft lithography techniques using replica molding comprised of two
layers of PDMS assembled on a glass cover slide. The valve operation to
control the chamber connections operates by filling control channels with either
water or air to create pneumatic or hydraulic pressure to provide a controllable
barrier valve, thereby opening or closing the microchannels that connect to the
chambers housing the cells.
Microfluidic platforms can be designed to support the culture of distinct cell
populations in close proximity. Figure 3.14 shows an example of co-culturing
of glial cells and neurons in microfluidic platforms. Using these platforms,
glial cells can be cultured in isolation from neurons until reaching near
confluence. Subsequently neuronal cells can be loaded into the other chamber
and attached while the barrier valve remains closed. By adding fresh neuronal
media to the chambers and opening the interconnection to allow flow of media
from one chamber to the other, glia-conditioned media can be provided to the
neurons.
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3.7.3 Self-assembled Networks
Research has shown it is possible to generate networks composed of
controllable low density neuronal cultures linked by bundles of axons and
dendrites with predesigned geometry and topology. Through manufacturing of
isolated islands of cell clusters surrounded by a non-adhesive background,
stable self-wired engineered networks of both cortical and hippocampal
neurons have been produced.
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Self-assembled networks often rely on the
natural tendency of cells to form ecient wiring between the closest neigh-
boring islands rather than on predesigned direction. Cell positioning within the
networks can be achieved through controlled network geometry, which can be
designed with wiring between cells consisting of axons and dendrites.
A template for the network in self-assembled cultures can be lithographically
defined, and the connectivity of the network is determined by the position of
the cultured clusters and islands of cells. Cells on these platforms, illustrated in
