High Throughput Techniques for the Investigation of Cell–Material Interactions - Biointerfaces: Where Material Meets Biology - page 262

have been identified that interact with integrins such as the arginine-
glycine-aspartic acid (RGD) peptide. This particular peptide represents a cell
attachment-mediating sequence present in Fn, and is known to promote cell
attachment when immobilised on surfaces. 31,33,35 Through careful tailoring
of biomaterial surface properties for the cell type of choice, the desired de-
gree of attachment, spreading or proliferation can be achieved. Conversely,
polymers such as polyethylene oxide (PEO), also known as PEG, have been
shown to minimise cell and biomolecule adsorption on a surface. 16,36-39 PEO
is particularly effective in regard to the reduction and prevention of protein
adsorption and, therefore, cell attachment, and this effectiveness depends
on the density, structure and molecular weight of surface immobilised
PEO. 40,41
In addition, it has been shown previously that the cellular response can be
directly influenced by surface topography alone. 42-45 Relevant topographical
characteristics including porosity, 5,46-48 grooved surfaces 49,50 and surface
roughness 25,51,52 have been demonstrated to influence the cellular response.
For example, ridges (2 mm wide and 3-5 mm high) have been formed on
surfaces and 95% of cells were observed to grow along the axis of these
ridges, regardless of any additional chemistry applied to the surface. 42
Commonly termed 'contact guidance,' this phenomenon has been used to
direct cell growth. Similarly, Teixeira et al. 43 found that keratocytes and
fibroblast cell lines aligned themselves along pre-formed grooves on the
substrate. Human neuroblastoma cells were found to selectively attach to
the coated regions. In another study, patterned poly- L -lactide (PLLA) films
were prepared to investigate the differentiation of multipotent mouse bone
marrow stromal precursors. 53 It was found that the presence of evenly
spaced 3 mm groves on the surface led to faster cell attachment and dif-
ferentiation after 10 days compared to flat PLLA films.

d n 3 r 4 n g | 7

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10.1.2 Stem Cell-Material Surface Interactions
Researchers are increasingly turning their attention towards stem cell re-
search for its obvious potential benefits in regenerative medicine appli-
cations. 54,55 Stem cells are particularly sensitive to substrate characteristics
due to their inherent capability to differentiate into more mature cell types.
Hence, through the careful tailoring of surface properties, a bias towards a
certain stem cell lineage may be generated. The ability to control differen-
tiation is expected to find a plethora of applications in tissue engineering
and regenerative medicine.
The cellular response to biomaterial surfaces, such as attachment and
proliferation, is known to be mediated by the material's surface chemistry.
Indeed, surface chemistry is also able to instruct cell function and direct
cell differentiation. 56-63 However, it has proven dicult to predict cell fate
outcomes based on the molecular composition of the polymer sub-
strate. 58,64 Recent work on carboxylic acid based plasma polymer (octa-
diene-acrylic acid) gradient surfaces demonstrated a relationship between