Biomedical Engineering Reference
In-Depth Information
a
b
PDMS
Seal stamp
on slide
c
PDMS
Glass
30
d
Flow agarose
Remove stamp
Singles
Pairs
*
Agarose
20
10
Adsorb FN
Seed cells
0
0 2
Distance (µm)
FIGURE 6.14
Cellular. micropattern. to. engineer. cell-cell. contacts.. (From. Celeste. M.. Nelson. and.
Christopher.S..Chen,.“Cell-cell.signaling.by.direct.contact.increases.cell.proliferation.via.a.PI3K-
dependent.signal,”.
FEBS Lett.
.514,.238-242,.2002..Adapted.with.permission.from.Elsevier..Figure.
contributed.by.Chris.Chen.)
spatial restriction contained either no gap, a 2-μm gap, or a 5-μm gap (the gaps were illed with
agarose, so cells would not spread over it). Intercellular adhesion molecules expressed in these
cells, including connexin 43, N-cadherin, VE-cadherin, and β-catenin, were found to localize to
cell-cell contacts within 4 hours ater plating onto the bow tie micropatterns. Proliferation for
pairs of cells on bow tie patterns without a gap was almost triple as proliferation for pairs of cells
(or single cells) on bow tie patterns with a 2-μm gap (
Figure 6.14d
).
Note that surface micropatterns are limited to adherent cells. A direct cell trapping method
is required to control the contact between nonadherent cells. A variety of other methods are
available for trapping pairs of cells using microwells (at random, thus many wells have single
occupancies or are occupied by two of the same cell type, see Section 5.3.2) and using hydrody-
namic weirs or microtunnels, which trap exactly two cells (see Section 5.3.6).
6.3.2 Control of Cell-Cell Spacing Using Micromechanical Actuators
In cellular micropatterns, the cell-cell spacing is ixed by design and cannot be changed once
the cells are seeded, which limits the range of questions that can be studied with patterning
technologies. During development, wound healing, or tumor growth, for example, the cells rely
on cell-cell communication and larger-scale tissue-level processes in which not only space but
also
time
is of the essence. To control the time parameter in cellular micropatterning experi-
ments, Sangeeta Bhatia's group, then at the University of California (San Diego), microfabri-
cated interlocking combs whose ingers it into each other (
Figure 6.15
). he combs, etched in
silicon, were spin-coated with polystyrene, resulting in a surface comparable to tissue culture
plastic. he slope of the tapered comb ingers results in a 20:1 mechanical transmission ratio;
that is, sliding the parts 1.6 mm changes the gap between the ingers by only 80 μm. he combs
can be manually “clicked” into a position in which the gap between the ingers is at one of
several notched spacings (~80-400 μm). By seeding diferent cell types on the two diferent
honeycombs, it is possible to study how the two cell types interact across the gap (which can be
changed) via soluble factors at any time set by the user. he positioning resolution is extremely
