Biomedical Engineering Reference
In-Depth Information
gelatin [619-624], PPF [625-627], polyamide [310, 311, 628-639],
PVA [340, 341, 640-642], PVAP [345], poly(ethylene-
-acrylic) acid
[643, 644], chitosan [645-651] and its derivatives [652], konjac
glucomannan + chitosan [653], PHEMA + PCL [654], PCL [390, 435,
655, 656], cellulose [70, 71, 657-659], Ti [660-662], PCL semi-
interpenetrating biocomposites [663] and many other biocompatible
hybrid formulations [279, 320, 335, 417, 664-683]. Furthermore,
each from the aforementioned formulations might be covered by a
layer of nanodimensional calcium orthophosphate, as it was done
by Zandi et al. [684], who coated a biocomposite of nano-sized
rods HA with gelatin by nano-sized HA. Several nanodimensional
biocomposites were found to be applicable as carriers for delivery of
drugs and growth factors [38, 685-687], as well as promising vectors
with ultrahigh gene loading and transfection efficiency [688]. Data
are available on the excellent biocompatibility of such biocomposites
[605]. The dispersion state of nano-sized particles appears to be
the critical parameter in controlling the mechanical properties of
nanodimensional biocomposites, as nano-sized particles always tend
to aggregate owing to their high surface energy [417]. A comparison
was made of the mechanical properties of biocomposites with nano-
sized and micron-sized HA with a polyamide. The results showed
that the bending and tensile strengths of the biocomposite increased
with increasing content of nanodimensional HA but decreased with
increasing micron-sized HA content [310]. A SEM image of the
mineralized collagen fibrils, demonstrating homogeneity of the
nanodimensional biocomposite and the close interaction between
the mineral phase and the reconstituted collagen fibrils, is shown in
Fig. 6.3 [689].
Porous (porosity ~85%) biocomposites of nano-sized HA with
collagen and PLA have been prepared by precipitation and freeze-
drying; these biocomposites did not show a pH drop upon
co
in vitro
degradation [608-610]. They were implanted in the radius of
rabbits and showed a high biocompatibility and partial resorption
after 12 weeks. Nano-sized HA/сhitosan biocomposites with
improved mechanical stability were prepared from HA/сhitosan
nano-sized rods [690]. Nano-sized HA/PLLA biocomposites of high
porosity (~90%) were prepared using thermally induced phase
separation [691]. Besides, nanodimensional HA was used to prepare
biocomposites with PAA and the nanostructure of the resulting
nano-sized crystals exhibited a core-shell configuration [692, 693].
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