Biomedical Engineering Reference
In-Depth Information
function. As for the studies on ECs and SMCs outlined above, emphasis has
been placed on cellular adhesion, alignment, elongation and contact guidance
on a variety of substrate materials with micro-grating topographies.
75,76
For
example, Lee et al.
77
studied the influence of micro-grating dimensions on the
behavior of FCs cultured on Ti substrates and demonstrated that micro-
gratings of Ti with widths of 10 and 30 mm, as well as a depth of 3.5 mm,
increased the cell viability, proliferation and up-regulation of fibronectin and
integrin genes. In addition, human FCs elongated and aligned better on the
micro-grated Ti substrates compared with the smooth Ti surfaces. An
analogous result was obtained in work on FC response to grating patterns in
the nanometer to micron range on PDMS surfaces.
78
Loesberg et al.
79
showed
that a lower threshold in grating depth (35 nm) induced the alignment and
orientation of FCs. They also reported that gratings of depths less than 35 nm
and widths less than 100 nm resulted in no cell alignment. Similarly, Sun et al.
80
studied the geometrical control of FCs on proton micro-machined 3D PMMA
scaffolds.
Many studies have been conducted on FC response to nano-island geometry.
Berry et al.
81
demonstrated increased FC adhesion, spreading, morphology and
cytoskeleton organization on nylon tubes exhibiting an internal nano-
topography generated through polymer de-mixing. Similarly, Dalby et al.
82-85
in a number of works reported a wide range of FC responses to nano-island
topographies with heights of 10, 13, 27, 35, 45, 50 and 95 nm that were also
created using polymer de-mixing. The 10, 13 and 27 nm islands increased FC
adhesion, proliferation, cytoskeletal development and up-regulation of gene
expression. Cell adhesion and proliferation on the 95 nm islands were reduced
and the cells displayed the most stellate morphologies with poorly formed
cytoskeletons. Cells on the 35, 45, and 50 nm island surfaces had the same
surface area as cells on flat controls, but with a less developed cytoskeleton.
These studies highlight the fact that slight changes in feature height can
produce very varied cellular responses. These experiments, however, did not
reveal why the cells showed increased or reduced adhesion and growth on the
different nano-islands. This type of surface structure created by polymer de-
mixing is limited to polymers.
Several studies have looked at the response of FCs to nano-pits. One such
study utilized arrays of nano-pits produced by e-beam lithography. The results
were increased cell spreading and filapodia interactions on 120 nm pits
compared with 75 nm pits, while cells on 35 nm pits had a similar number of
filopodia to those grown on control samples.
86
The effect of nano-post geometries on FC function has been the subject of
much study. Green et al.
87
found that posts of 2 and 5 mm heights resulted in
increased cell proliferation compared with 10 mm high posts and smooth
surfaces. Milner and Siedlecki
88
observed FC adhesion and proliferation on
PLA surfaces patterned with 400 nm and 700 nm posts via replication molding.
Their results demonstrated increased FC adhesion and decreased cell prolife-
ration on surfaces with 400 nm textures compared with 700 nm textures
and smooth surfaces. The effect of FC adhesion on polycarbonate and
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