Biomedical Engineering Reference
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P4HB patch for the augmentation of the pulmonary artery in sheep was
nearly completely resorbed within 24 weeks [42]. A similar result has been
reported with porous P4HB tubes replacing a part of the descending aorta
in sheep [262]. Compact P4HB films implanted s.c. in rats showed a mo-
lecular weight decrease to approximately 62%after10weekswhilehighly
porous P4HB samples were completely resorbed at that time. Films, 50%, and
80% porous samples showed a 20%, 50%, and 100% mass loss, respectively,
over the 10 week period. Microscopic examination revealed a progressive sur-
face erosion starting with signs of cracking after 1 week. On the other hand,
in vitro samples showed almost no discernable change during 10 weeks of
incubation in buffer solution, suggesting a biologically mediated mode of
degradation in vivo [56].
P4HB films tested as aortic patches in rabbits showed progressive signs of
degradation, confirming a surface erosion mechanism (Fig. 15); films made of
Fig. 15 P4HB films (6 × 2 mm) implanted into the infrarenal aorta of rabbits 26 weeks post-
operatively (H&E, 400
). a Nearly complete film degradation in one animal. b Surface
erosion and beginning film fragmentation in another animal. The inflammatory response is
focal and appropriate at this stage of polymer resorption, with the number of macrophages
surrounding the film remnants dependant on the degradation progress [263]
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