174 K.Yu,G.GaoandJ.N.Kizhakkedathu
on the surface (linear vs. branched), chemistry of the polymers and molecular
weight of the grafted chains.
This chapter is organized based on the application of different polymers and
approaches used for the development of anti-fouling coatings.
8.2 NON-FOULING SURFACES BASED ON POLY(ETHYLENE
GLYCOL)
Poly(ethylene glycol) (PEG) or polyethylene oxide (PEO) has been widely used
for the development of non-fouling surfaces because of its capacity to resist the
attachment of cells and proteins.
36
It is also nontoxic and nonimmunogenic.
36
PEG is composed of -CH
2
-CH
2
-O- repeating units with a hydroxyl group at each
end of the polymer chain. The mechanisms of the antifouling ability of PEG are
not fully understood. It is believed that the antifouling ability of PEG is due to
the combined effects of steric repulsion, large excluded volume, configurational
entropy, hydrated chain mobility, molecular weight and surface coverage.
4,19,3739
Several surface modification approaches have been reported for the devel-
opment of PEG surfaces. We can classify these methods in terms of the at-
tachment strategies; physical adsorption vs. chemisorption, self assembly vs.
covalent attachment etc. Each method has its own advantages or disadvantages
depending on the ease of the synthesis or its performance. The physical adsorp-
tion of PEG-containing copolymers,
4048
oligo(ethylene glycol)-terminated self-
assembled monolayers (SAMs),
4965
grafted polymers based on PEG,
6681
and
surface initiated polymerization of a PEG-containing monomer
8290
are the most
commonly used approaches for the development of PEG surfaces. In the following
section we will discuss different strategies adopted for the development of PEG
grafted surfaces.
8.2.1 Physical Adsorption of PEG-containing Copolymers
8.2.1.1 Hydrophobic Adsorption
This method allows the attachment of PEG chains to a variety of surfaces solely
based on the hydrophobicity of the material. One example is the use of triblock co-
polymer, polyethylene glycol-b-polypropylene oxide-b-polyethylene glycol (PEG-
b-PPO-b-PEG)
40
that assemble spontaneously on hydrophobic surfaces through
hydrophobic-hydrophobic interactions. This class of polymer is also known as
poloxamers or pluronics and has been extensively studied
4145
Liu and Bhatia
reported an application of a commercially available, PEG-terminated triblock poly-
mer (Pluronic™F108) to create nonadhesive domains on a variety of biomaterials
that prevented cell adhesion for up to four weeks in culture medium.
45
They also
demonstrated the ability to micropattern the growth of murine fibroblasts in 5%
serum and retained cell-free domains for up to four weeks on polystyrene. The
pluronics was also shown to adsorb to a variety of surfaces including tissue culture
plates, methylated glass, silicone and polylactic-co-glycolic acid.
45
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