Biomedical Engineering Reference
In-Depth Information
Kushiro and Asthagiri
2012
), substrates stiffness (Lo et al.
2000
; Kidoaki and
Matsuda
2008
; Frey and Wang
2009
), parallel multiple grooves (Kaiser et al.
2006
;
Fraser et al.
2008
; Uttayarat et al.
2005
; Hu et al.
2005
; Clark et al.
1990
; Kim et al.
2009a
; Tan and Saltzman
2002
), micropillars (Ghibaudo et al.
2009
; Frey et al.
2006
), and square lattice pattern arrays (Kim et al.
2009b
) are shown to affect speed
and orientation of cell migration.
As well as micro- and nanofabrication techniques, cell-based assay techniques to
evaluate the effectiveness of the substrates on cells are critical to develop advanced
strategy of cell migration control. One major technique is based on a static analysis
of cells that attain a temporally homogenous state after being exposed to a guiding
cue. Another and more advanced technique is dynamic analysis that focuses on
transient changes in the behavior of cells. This approach is expected to elucidate
potential effects, which might be overlooked by the static analysis, to control cell
migration. Thus, this chapter deals with the dynamic analysis.
Substrate topography is extensively studied, and has great latent potential of
application to the design of biomaterials. Topographical cues are purely physical
and biologically non-invasive (Lim and Donahue
2007
). Furthermore, they are stable
against non-specifi c adsorption of proteins from the media and/or that secreted
from the cells (Kim et al.
2009a
). Static analyses with slowly migrating cells in a
temporally homogenous state have shown that multiple parallel grooves are a simple
and effective topographical feature for cell migration control. In this case, cells
orient and migrate predominantly along the anisotropic direction of the grooves,
and the magnitude of cell response is affected by the density of grooves, and
probably by the fl exibility of the cytoskeleton of cells (Fraser et al.
2008
; Uttayarat
et al.
2005
; Hu et al.
2005
; Clark et al.
1990
; Kim et al.
2009a
; Clark
1994
; Curtis
and Wilkinson
1997
).
In this chapter, we fi rst explain typical micro- and nano-fabrication techniques to
provide topographical features of a substrate that is used for cell culture. Next, we
describe cell-based assay that adopts the dynamic analysis with focus on changing
behavior of cells in response to micro-topographical cue. In the analysis, the effects
of a single line groove are discussed in order to understand the fundamental effect
of microgrooved structure. Then, we show how the effect of the single line groove
is altered in the intersecting grooves. Finally, we derive functions of the grooved
surfaces as a repellant and a trap of migrating cells, and further provide design cri-
teria of the functional surfaces.
9.2
Techniques to Fabricate Microstructured Surfaces
Extracellular matrix typically includes the components on the order of nano- to
micrometer scale as discussed in detail in Sect.
10.2.1
of Chap.
10
. The topographi-
cal features on these length scales have a great impact on cell behaviors.
Microelectromechanical systems (MEMS) fabrication techniques, which were orig-
inally developed in the semiconductor and microelectronics industries, can con-
trol substrate features at length scales from sub-micrometers to hundreds of
