Biomedical Engineering Reference
In-Depth Information
Fig. 8
Rhodamine-phalloidin staining of the F-actin of SMCs on a PDMS substrate. Area 1 is
patterned with 48-mm wide channels. Area 2 is unpatterned. The
white arrows
indicate the border
between the two surfaces. The actin in the cells in area 1 have a high order of alignment while those
on area 2 have a random network of actin fi laments that are not organized as a population
All channel widths investigated aligned the SMCs in relation to the pattern.
Quantifi cation of the alignment showed 95% alignment on the microfabricated sub-
strates. The aspect ratio (the ratio of the long axis of the cell to the short axis) was
signifi cantly different on each of the channel widths. Cells on the thinnest channels had
an aspect ratio (~14) comparable to SMCs found in vivo. Immunofl uorescence staining
also showed a highly aligned F-actin network in the cells. Smooth muscle cells grown
on fl at PDMS substrates had no organization and had very unordered F-actin networks.
This is very important because alignment of the actin cytoskeleton is required for direc-
tional contraction. By aligning the network of actin fi laments throughout the popula-
tion of cells, the entire unit will act to contract in a single direction (Fig.
8
).
An important part of these stacked membranes will be the ability for nutrients to
diffuse in through the layers and cellular waste to diffuse out so the cells in interior
layers can survive. In traditional scaffolds, where the volume of the scaffold is made
from one piece of material instead of being built up layer by layer, diffusion of
nutrients to the center of the scaffold is accomplished through a porous network in
the material. Without creating a porous network between the layers in the stacked
membranes, the patterned cells in the interior of the construct will die due to inad-
equate nutrient supply. Creating this porous network will require creating holes in
the membranes that will act as the pores. The topography of the membranes, how-
ever, is the key to organizing the cells in the appropriate manner. Disruption of
the surface topography with pores could lead to a loss in cell patterning. The pores
