Biomedical Engineering Reference
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anhydride [355] and β-TCP/PLLA [462] biocomposites, in which
weak chemical bonds were considered to form between Ca
2+
ions
located on the HA, CDHA, ACP or β-TCP surface, respectively, and
slightly polarized O atoms of C=O bonds in the surrounding bioorganic
compounds. The data obtained suggest that crystallization of calcium
orthophosphates in chitosan-containing solutions is substantially
modulated by a chemical interaction of the components; apparently,
a part of calcium is captured by chitosan and does not participate in
the formation of the main mineral phase [1136]. Schematically, this
type of the chemical interaction is shown in Fig. 6.7 [709].
Figure 6.7
A schematic diagram of Ca 2+ ion binding with alginate chains.
Reprinted from Ref. [709] with permission.
Except of FTIR spectroscopy, other measurement techniques are
also able to show some evidences of a chemical interaction among the
phases in calcium orthophosphate-based biocomposites and hybrid
biomaterials [345, 462, 635, 638, 641, 1134-1138]. For example,
for nano-sized crystals of CDHA/alendronate such evidences were
observed by thermogravimetric analysis: DTG plots of the crystals
appeared to be quite different from those obtained from mechanical
mixtures of CDHA and calcium alendronate with similar compositions
[1137]. Analogous DTG results were obtained for nano-sized HA/PVA
biocomposites [641]. In the case of biocomposites of nano-sized HA
with polyamide, a hydrogen bonding among the phases was detected
by differential scanning calorimetry technique [635]. Another
example comprises application of the dynamic mechanical analysis
to investigate softening mechanism of β-TCP/PLLA biocomposites
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