Biomedical Engineering Reference
In-Depth Information
358] have been already developed. Namely, PVA/CDHA biocomposite
blocks were prepared by precipitation of CDHA in aqueous solutions
of PVA [318]. An artificial cornea consisted of a porous nano-sized
HA/PVA hydrogel skirt and a transparent center of PVA hydrogel has
been prepared as well. The results displayed a good biocompatibility
and interlocking between artificial cornea and host tissues [340,
341]. PVAP has been chosen as a polymer matrix, because its
phosphate groups can act as a coupling/anchoring agent, which has
a higher affinity toward the HA surface [345]. Greish and Brown
developed HA/Ca poly(vinyl phosphonate) biocomposites [349-
351]. A template-driven nucleation and mineral growth process for
the high-affinity integration of CDHA with PHEMA hydrogel scaffold
has been developed as well [358].
PEEK [225, 227, 359-365, 367] and HIPS [366] were applied
to create biocomposites with HA having a potential for clinical
use in load bearing applications. The study on reinforcing PEEK
with thermally sprayed HA particles revealed that the mechanical
properties increased monotonically with the reinforcement
concentration, with a maximum value in the study of ~40% volume
fraction of HA particles [361-363]. The reported ranges of stiffness
within 2.8-16.0 GPa and strength within 45.5-69 MPa exceeded
the lower values for human bone (7-30 GPa and 50-150 MPa,
respectively) [362]. Modeling of the mechanical behavior of HA/
PEEK biocomposites is available elsewhere [364].
Biodegradable poly(α-hydroxyesters) are well established in
clinical medicine. Currently, they provide with a good choice when
a suitable polymeric filler material is sought. For example, HA/PLGA
composites were developed which appeared to possess a cellular-
compatibility suitable for bone tissue regeneration [368-376].
Zhang and Ma seeded highly porous PLLA foams with HA particles
in order to improve the osteoconductivity of polymer scaffolds for
bone tissue engineering [52, 292]. They pointed out that hydration
of the foams prior to incubation in simulated body fluid increased
the amount of carbonated CDHA material due to an increase of
COOH and OH groups on the polymer surface, which apparently
acted as nucleation sites for apatite. The following values of Young's
modulus, compressive, bending, and tensile strengths for PLLA/HA
composites have been achieved: 5-12 GPa, 78-137 MPa, 44-280
MPa, and 10-30 MPa, respectively [377]. However, these data do not
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