Biomedical Engineering Reference
In-Depth Information
mesenchymal stem cells (hMSCs) (Figure 10.3C). One thousand, seven
hundred spots of differing polymer compositions and molecular weights
were deposited onto poly(hydroxyethyl methacrylate) (PHEMA) coated slides.
PHEMA has been shown to inhibit cell binding and hence was expected to
stop cell binding between polymer spots. Polymer compositions were iden-
tified that promoted cell attachment and spreading of hMSCs and polymer
properties were identified which allowed for high levels of differentiation
into cytokeratin-positive cells. Mant et al.
81
also investigated cellular re-
sponse to a variety of polyurethane polymers. One hundred and twenty
different polyurethane combinations were prepared in a microarray format
to identify polymers that promoted cell attachment of bone marrow den-
dritic cells. All polymer compositions that promoted cell attachment were
found to contain poly(tetramethylene glycol). Flaim et al.
82
have also pre-
pared a microarray to investigate different combinations of five extracellular
matrix proteins (collagen I, collagen III, collagen IV, Fn and laminin) on the
attachment of rat hepatocytes and mouse embryonic stem cells, observing
that collagen III showed the highest cell attachment, whilst laminin showed
the lowest cell attachment.
Although a broad spectrum of surface properties have been investigated
using the microarray format, the majority of experiments were conducted
using different samples for every variant of every parameter, e.g., polymer
composition. However, an alternative high-throughput technique, gradient
surfaces, allows for the optimisation of a limited set of parameters in a single
experiment. Surface chemistry and topography gradients are a format that is
particularly well suited to study subtleties in cell response to surface topo-
graphy or chemistry. The format permits one variable, such as functional
group density, to be continuously changed with respect to the position on a
test surface whilst other parameters are held constant.
11,22,83,84
This plat-
form also requires significantly lower cell numbers, lower quantities of
culture medium and sample materials in comparison to the testing of sur-
face chemical properties with discrete samples.
d
n
3
r
4
n
g
|
7
.
10.2 Gradient Surfaces
A gradient can be defined as a surface with continuously varying chemical
composition along one dimension, or a transition from one surface property
to another.
11,22,85
Gradient surfaces were first described in 1987 by Elwing
et al.
86
who created methylsilane wettability gradients to investigate the ef-
fect of wettability on protein adsorption. However, since this time many
gradients based on topography, polymer compositions, elasticity and bio-
molecule density have been formed.
5,22,87,88
There have been several detailed
review articles published surrounding the preparation of topography and
chemical gradients in recent years.
11,22,79,83,84
A summary of some of the
gradient preparation techniques is shown in Figure 10.4. This section
highlights some of the fundamental and recent developments in the field of
gradient surface preparation.
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