Biomedical Engineering Reference
In-Depth Information
properties.
91
langer and coworkers
89-91
developed poly(anhydride-
co
-imides)
(fig. 6.7) that were compression-molded into circular discs, then implanted in
rat subcutaneous tissues for nearly two months. the polymer matrices support
endosteal and cortical bone regeneration and show minimal inflammation with
dense fibrosis. Matrices degraded slowly and maintained their shapes over
the period studied, displaying compressive properties similar to cancellous
bone and thus being promising as devices for orthopedic applications.
90
the main limitation of polyanhydrides is their lack of storage stability,
requiring storage under refrigeration. these polymers undergo spontaneous
depolymerization to low molecular weight polymers in organic solutions or
upon storage at room temperatures and above.
93
6.5 Fumarate-based polymers
the development of fumarate-based polyesters for biomedical applications
started around 20 years ago. fumaric acid is a natural metabolite involved
in Krebs cycle, and is comprised of a reactive double bond available for
chemically crosslinking reactions. these characteristics make fumaric acid
a candidate building block for crosslinkable polymers. The first and most
comprehensively investigated fumarate-based copolymer is the biodegradable
copolyester poly(propylene fumarate) (PPf) (fig. 6.8).
3
O
N
CH
2
O
O
O
O
6
O
O
O
O
O
n
m
O
O
O
N
O
6
O
O
O
O
O
n
O
m
6.7
Poly[trimellitylimidoglycine-co-1,6-bis(
p
-carboxyphenoxy)hexane]
developed for subcutaneous implantation.
92
O
O
HO
O
OH
O
n
6.8
Polypropylene fumarate.
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