AAWSAP DIRD, Biomaterials, January 2010

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tissues. The barrier remains in place only for a week or so during the healing process
before biodegrading so no foreign body is le~ inside of the body.
POLYETHYLENE GLYCOL OR
POLYETHYLENE OXIDE
Polyethylene glycol (PEG) is a widely
used material in biomedicine,
pharmaceuticals, cosmetics, and
agriculture. Its chemical compatibility,
water solubility, nontoxicity,
biocompatibility, and multiple physical
states allow it be used as coatings and
in solid form to create surfaces that
are very acceptable to biology. Figure
13 shows the marketing of PEG to
broad markets that include
biodegradable polymers.
One of PEG's major applications is in
the creation of "nonfouling" surfaces
when exposed to blood or biological
environments. The nonfouling, or cell­
and protein-resistant, properties of
surfaces containing PEG are due to the
material's highly hydrated state.
Figure 13. Biodegradable Polymers Based on
Copolymers of Polylactic Acid and Polyethylene Glycol
PEG is used in drug delivery systems
to improve the solubility of drugs and to help stabilize immunogenic or unstable protein
drugs. This can enhance the circulation times and stabilities of drugs in the body.
HYDROGELS
Hydrogels are liquid or semisolid
materials that have a strong affinity
for water. Poly(hydroxyethyl
methacrylic) acid, or poly(HEMA), is
one of the most important hydrogels
in the biomaterials world because it
has many advantages over other
hydrogels. These include a water
content similar to living tissue,
inertness to biological processes,
resistance to degradation,
permeability to metabolites, and
resistance to absorption by the body.
Poly(HEMA) can easily be
manufactured into many shapes and
forms and be easily sterilized . This is
due to its structure, which is
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Figure 14, Dots of Hydrogel
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