Biomedical Engineering Reference
In-Depth Information
9.2.2
Etching
After photolithographic patterning (UV exposure and development), the substrate
area uncovered with the photoresist is selectively etched. In our case explained here,
the silicon top surface is vertically etched to a depth of 20
m, as shown in Fig.
9.1d
,
by using deep reactive ion etching (DRIE) method. Then, the photoresist is removed
by ashing with oxygen plasma. The fabrication process is completed by growing
SiO
2
on the substrates by thermal oxidation.
Dry etching processes usually results in square cross sections, whereas wet
chemical etching usually gives V-shaped structures depending on the type of etchant
and crystal orientation of silicon substrate.
μ
9.3
Effect of Single Line Groove on Single Cell Migration
This section describes the effect of a single line groove on the transient change in
migratory behavior of a fi sh epidermal keratocyte encountering a single line groove.
First, methodology of cell migration assay to demonstrate the change in migratory
behavior is presented in Sect.
9.3.1
. Then the result of the assay, and the effect of a
single line groove on cell migration are described in reference to the result of the
cell migration assay in Sect.
9.3.2
.
9.3.1
Cell Migration Assay
This section describes a method of cell migration assay using fi sh epidermal keratocytes
as models. Since silicon offers precise fabrication of grooved substrates, it is suitable
as a material of a test substrate for investigating the effect of micrometer-order size
difference on cell migration. Because fi sh epidermal keratocytes exhibit rectilinear
migration and have a simple shape (Fig.
6.1a
in Chap.
6
)
, migrating keratocyte is a
suitable model for reproducible evaluation of the effectiveness of an engineered
substrate on cell migration control.
9.3.1.1
Cell Culture Substrate
Silicon microstructured surface for the cell migration assay can be fabricated
according to the method described in Sect.
9.2
. The dimension of the substrate is
shown in Fig.
9.2
. In the analysis described here, the groove depth was fi xed to be
20
μ
m. The groove width was 1.5
μ
m (L-W1.5), 4
μ
m (L-W4), or 20
μ
m (L-W20).
The width of 1.5
μ
m is small compared with the size of a cell nucleus; 4
μ
m is
comparable to the size of a cell nucleus, and 20
m is comparable to the size of a
keratocyte's lamellipodium from front to back (7-15
μ
μ
m) (Laurent et al.
2005
).
