Biomedical Engineering Reference
In-Depth Information
werealsoimprovedintermsofbioactivityandosteoblastresponses
with the incorporation of small amounts of the bioactive nanocom-
ponent. One chief merit of the nanocomponent is that complex-
shaped composites, such as 3D scaffolds, are possibly produced
withoutdisintegrationofthemorphology,whichconsequentlyleads
to improvement in the bioactivityand mechanical properties.
14.3.3
Composite Nanofibers
Bone is a kind of nanocomposite, consisting of a collageneous
fiber network and embedded calcium phosphate (mostly hydrox-
yapatite) nanocrystallites. Thus combining the polymeric phase
with bioactive inorganics is considered an appropriate way to bet-
ter mimic the composition and structure of the bone matrix.
32
For successful electrospinning of polymer-inorganic composites,
the properties of the solution should be carefully tailored and
considered.
Recent studies have focused on the preparation of composite
nanofibers by electrospinning. One elegant approach was made
in the gelatin-hydroxyapatite composite.
33
Hydroxyapatite crystals
were first prepared in the presence of gelatin by the precipitation
of calcium and phosphorus precursors, resulting in a nanocom-
posite precipitate. Using transmission electron microscopy, bone
mineral-like nanocrystallites were observed to be well dispersed
andorganized,whichwasfacilitatedbythenucleationroleofgelatin
amino acids (Fig. 14.4). After dissolving the nanocomposite pre-
cipitate in a solvent, it was possible to electrospin nanofibers con-
taining 20% and 40% hydroxyapatite with fiber sizes of a few
hundreds of nanometers. Compared with the gelatin nanofiber, the
nanocomposite nanofibers showed better osteoblastic differentia-
tion behavior, while preserving mechanical integrity. Using a sim-
ilar approach, a hydroxyapatite-collagen nanofiber, which was to
mimic the bone ECM, was also produced.
34
Moreover, a chitosan-
hydroxyapatite nanofiber was developed as a functional bone
matrix.
35
Bioactive inorganics were also added to some synthetic
polymers during the electrospinning.
36
,
37
In this case, however, the
innate hydrophobicity of polymers hampered the involvement of
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