Biomedical Engineering Reference
of 50% at-P3HB in the blend did not further accelerate the degradation of
P3HB implants reinforced with carbon fiber for fixation of tibial osteo-
tomies in rabbits were completely resorbed 24 weeks after implantation .
In contrast, P3HB used for bone regeneration of mandibular defects in rats
did not show any signs of degradation in the 6-month study . Exami-
nations of P3HB/HA composites implanted in the femur of rabbits showed
physical cracks after 3 months but no signs of resorption . However, a de-
grading P3HB phase was observed at the interface between bone and pins
made of P3HB or P3HB/HA after 6 months of implantation into condyles
of rabbits . P3HB screws implanted for 2 years intramedullary in sheep
showed a slight reduction of hardness . An almost completely resorbed
osteosynthesis screw made of P3HB-15%3HV was found after 32 months of
subfascial implantation in the sheep, whereas other implants, among them
some made of P3HB homopolymer, showed no signs of resorption at this
time. However, a large numeric difference between implanted and explanted
samples was observed. Thus, in one sheep, despite a most thorough investiga-
tion, only 3 out of 15 implants could be retrieved .
Applications in Tissue Engineering
P3HB patches have shown potential for guided tissue regeneration in a num-
ber of animal studies and in patients. Nonwoven P3HB patches made from
solution-spun fibers have been extensively studied for defect repair in heart
surgery, such as for pericardial substitution [32, 33, 142, 143, 204, 211-213],
for closure of atrial septal defects , and for enlargement of the right ven-
tricular outflow tract and the pulmonary artery .
Pericardial adhesions following open-heart surgery, which may severely
complicate cardiac reoperations, were minimized and the coronary anatomy
was preserved after implantation of a nonwoven P3HB patch in sheep for
up to 30 months. The patch surface was shown to support regeneration of
mesothelial cells with preserved prostacyclin activity [142, 211]. However,
when tested after cardiopulmonary bypass surgery, which causes additional
insult to the pericardium, implantation of P3HB pericardial patches did not
affect adhesion formation or postoperative coronary anatomy visibility in
a short-term study in sheep .
P3HB pericardial patches have been tested in a randomized clinical study
and significantly limited retrosternal adhesions after cardiac surgery .
Another clinical report confirms the potential of P3HB pericardial patches
for pediatric patients undergoing open heart surgery to repair congenital de-
fects . However, the patch does not affect postoperative changes in the
right ventricular function after coronary artery bypass surgery .