Biomedical Engineering Reference
In-Depth Information
Along this line, PCL is used as a slowly biodegradable but well-
biocompatible polymer. PCL/HA and PCL/CDHA biocomposites
have been already discussed as suitable materials for substitution,
regeneration, and repair of bone tissues [328, 420-433]. For example,
biocomposites were obtained by infiltration of ε-caprolactone
monomer into porous apatite blocks and
polymerization
[423]. The composites were found to be biodegradable and might
be applied as cancellous or trabecular bone replacement material or
for a cartilage regeneration. Both the mechanical performance and
biocompatibility in osteoblast cell culture of PCL were shown to be
strongly increased when HA was added [434]. Several preparation
techniques of PCL/HA biocomposites are known. For example, to
make biocomposite fibers of PCL with nanodimensional HA, the
desired amount of nanodimensional HA powder was dispersed in a
solvent using magnetic stirrer followed by ultrasonication for 30 min.
Then, PCL was dissolved in this suspension, followed by the solvent
evaporation [435]. The opposite preparation order is also possible:
PCL was initially dissolved in chloroform at room temperature
(7-10% weight/volume), then HA (~10 µm particle size) was
suspended in the solution, sonicated for 60 s, followed by the solvent
evaporation [160] or salt-leaching [436]. The mechanical properties
obtained by this technique were about one-third that of trabecular
bone. In a comparative study, PCL and biological apatite were mixed
in the ratio 19:1 in an extruder [437]. At the end of the preparation,
the mixture was cooled in an atmosphere of nitrogen. The authors
observed that the presence of biological apatite improved the modulus
while concurrently increasing the hydrophilicity of the polymeric
substrate. Besides, an increase in apatite concentration was found to
increase both the modulus and yield stress of the composite, which
indicated to good interfacial interactions between the biological
apatite and PCL. It was also observed that the presence of biological
apatite stimulated osteoblasts attachment to the biomaterial and cell
proliferation [437]. In another study, a PCL/HA biocomposite was
prepared by blending in melt form at 120 ºC until the torque reached
equilibrium in the rheometer that was attached to the blender [438].
Then the sample was compression molded and cut into specimens
of appropriate size for testing. It was observed that the composite
containing 20 wt.% HA had the highest strength [438]. However, a
direct grafting of PCL on the surface of HA particles seems to be the
most interesting preparation technique [420]. In another study, HA
in situ
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