Biomedical Engineering Reference
In-Depth Information
biomaterials. The degradation mechanism is hydrolytic chain scis-
sion, similar to poly(
α
-hydroxy ester). The mechanical strength and
degradable behaviors were controlled by the reaction of cross-
linking with vinyl monomer to unsaturated double bonds. Also, the
physical property will be enhanced by the composite with degrad-
able bioceramic
-tricalcium phosphate for the application of the
injectablebone.
17
Copolymerizationofpropylenefumaratewitheth-
ylene glycol can be endowed with the elasticity of poly(propylene
fumarate) for the cardiovascular stent. New materials for propylene
fumarate polymers are continually investigated through copolymer
synthesis,hybrid composites, andblends.
β
1.2.3.4 PEO and its derivatives
Polyethylene oxide (PEO) is one of the most important and widely
used polymers in the biomedical applications due to its excellent
biocompatibility.
18
It can be produced by anionic or cationic poly-
merization from ethylene oxide by initiators. PEO is used in the
coating materials for the medical devices to prevent tissue and cell
adhesion as well as preparation of biologically relevant conjugate
and induction cell membrane fusion. PEO hydrogels can be fab-
ricated by the cross-linking reaction such as gamma ray, electron
beamirradiation,orchemicalreaction. Thishydrogelcanbeusedin
theapplicationofdrugdeliveryandtissueengineering.Thehydroxyl
in the glycol end group is very active, resulting in availability for
chemical modifications. Attachment of bioactive molecules such as
cytokinesandpeptidestoPEOorpoly(ethyleneglycol)(PEG)allows
to enhance the delivery e
ciency of bioactive molecules (detailed
explanation in section 1.3).
For the synthesis of biodegradable PEO, block copolymerization
with PGA or PLA degradable units has been carried out to make
biodegradable hydrogels. It can be polymerized as two- or three-
block copolymers such as PEO-PLA, PEO-PLA-PEO, and PLA-PEO-
PLA. For the biodegradable block,
ε
-caprolactone,
δ
-valerolactone,
PLGA, etc., can be used. The characteristic of these series hydro-
gels shows temperature-sensitive phenomena. Sol state at room
temperature changes to gel state at body temperature. Hence,
biodegradablehydrogelswereveryusefulforinjectablecell-loading
Search WWH ::
Custom Search