Biomedical Engineering Reference
In-Depth Information
up to 12 weeks [108, 146]. Few differences between P3HB-3HV copolymers in
terms of tissue response have been found after i.m. implantation of P3HB-
3HV (7%, 14%, 22% HV) in sheep for up to 90 weeks. Acute inflammatory
reactions significantly decreased with time and no abscess formation or tis-
sue necrosis were reported in this study [100]. The tissue response to P3HB
and P3HB-3HV (15% HV) fibers implanted i.m. in rats was characterized by
a short acute inflammation period (up to 2 weeks) followed by the forma-
tion of a fibrous capsule of less than 200
µ
m thickness during weeks 4 to 8,
which was reduced to 40-60
mafter4-6 months. Forty eight weeks after
surgery, the fibrous capsule surrounding the implants was minimal. Mono-
and polynuclear macrophages were still abundant at this time. The tissue
response to P3HB and P3HB-3HV fibers was similar in terms of inflamma-
tory reaction and fibrous capsule formation. There were no adverse reactions,
such as suppurative inflammation, necrosis, calcification, and malignant tu-
mor formation for up to 48 weeks after implantation [147, 148].
P3HB discs implanted for 3 months in the peritoneum of rats showed the
presence of a thin and poorly adherent fibrous capsule that contained no in-
flammatory cells. P3HB was assessed to be biocompatible because the formed
capsule was porous and ensured communication between the polymer and
the biological fluids. Perfluorohexane plasma-modified P3HB discs were sur-
rounded by a nonporous capsule indicating a slight decrease in the surface
biocompatibility [139].
P3HB samples implanted s.c. and i.p. in rats were found to be tissue com-
patible without inflammation reaction or tumor formation. After 1 year of
implantation the fibrous capsule surrounding the s.c. implant was about 30%
thicker than that surrounding the i.p. implant. A small number of phagocytes
indicated the polymer resorption process at that time [149].
No inflammatory reactions resulted from the i.m. injection of P3HB or
3HB in rats, indicating a good in vivo biocompatibility [119]. P3HB patches
implanted onto the rat stomach showed no significant inflammatory response
as confirmed by analysis of cytokine production. A group of mRNAs en-
coding pancreatic enzymes was transiently present in tissue surrounding the
patch material [150] 1-2 weeks after implantation. The amount of mRNA of
the inflammation marker C-reactive protein (CRP) was also found to tran-
siently increase [151].
P3HB in bone contact causes a strong initial cellular reaction with slight or
no inflammation [152]. P3HB bone screws showed an optimal tissue compati-
bility [153]. Osteosynthesis plates and screws made of P3HB were highly com-
patible without induction of immunologic or inflammatory reactions [154].
A very fast healing and formation of new bone substance could be achieved
with P3HB/HA composites [93]. The interface between the composite and
bone was physically and biochemically active over a 6-month period of im-
plantation into the condyles of rabbits. Bone bonding to these composites
occurred by degradation of the P3HB matrix, which led to the formation of
µ
