Biomedical Engineering Reference
In-Depth Information
applications such as delivery vehicles,
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nerve guides,
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,
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and
cell carriers forchondrocyte transplantation.
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8.3.1.2 Photo-cross-linkable hyaluronic acid
HA is a naturally derived nonimmunogenic, nonadhesive gly-
cosaminoglycan composed of D-glucuronic acid and
N
-acetyl-
D-glucosamine and is found in many connective tissues.
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HA undergoes enzymatic degradation
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,
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,
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and plays a
role in the promotion of cell motility and proliferation,
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,
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,
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,
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wound healing,
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,
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,
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angiogenesis,
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and the reduction of
long-terminflammation.
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,
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Itisattractiveforbiomaterialappli-
cations because it can be modified with various functional groups
so that covalent cross-linking reactions are possible.
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Smeds
et
al
.
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modified HA for photopolymerization with the addition of a
methacrylate group by reaction with methacrylic anhydride (Fig.
8.4b).
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They investigated the influence of the degree of methacry-
lationonbulkmechanicalpropertiessuchasswelling,compression,
and creep compliance. It was demonstrated that the hydrogels pre-
paredfrommethacrylatedHAarecapableofswellingupto14times
their dry weight and are stronger and more resilient than corre-
sponding alginate gels.
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8.3.1.3 Photo-cross-linkable chitosan
Chitosan is a partially deacetylated form of chitin, a natural linear
homopolymer of b-1,4-linked
N
-acetyl-D-glucosamine.
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Useful
advantagesofchitosanincludeitshemostaticactivity,
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immunolog-
ical activity, and ability to accelerate wound healing.
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It has been
modified by reaction with N,N,N',N'-tetramethylethylenediamine,
EDC, and 4-o-b-D-galactopyranosyl-(1,4)-D-gluconic acid to intro-
duce azide and lactose moieties for photo-cross-linking (Fig. 8.4c).
This modified chitosan (AZ-CH-LA) has primarily been investigated
as a tissue adhesive,
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,
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,
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and it has been shown that AZ-CH-
LA demonstrates higher binding strengths than fibrin glue and is
effective at sealing punctures in thoracic aorta and lungs in rab-
bit models.
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Azide-modified chitosan has also been investigated
as a matrix for drug delivery
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,
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and as a cell-seeded material
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