Biomedical Engineering Reference
In-Depth Information
3.6.5
Biomimetic Construction Using Nanodimensional
Particles
Morphological control of bioinorganic materials is another
interested issue in biomineralization, by which inorganic materials
with complex morphologies can be produced. Complex forms or
patterns with a hierarchical structure over several length scales
are important features of biomineralization. Pattern formation in
biomineralization is a process in which self-assembled organic
templates are transformed by a material's replication into organized
inorganic structures. Needless to mention, that researchers try to
reproduce these processes in laboratories. For example, Chen et
al
reported a way to create enamel-like structures by modifying
synthetic nano-sized rods of apatite with a surfactant, bis(2-
ethylhexyl)sulfosuccinate salt, that allowed the nano-sized rods to
self-assemble into prism-like structures at the water/air interface
[193]. A nanometer-scale rod array of apatite having preferred
orientation to the
.
-axis was successfully prepared simply by soaking
calcium-containing silicate glass substrates in Na
c
aqueous
solution at 80°C for various periods [491]. A biomimetic bottom-
up route to obtain the first hierarchical level of bone was reported
[182]. A pH-induced self-assembly of peptide-amphiphile to make
a nanostructured fibrous scaffold reminiscent of extracellular
bone matrix was obtained. After the cross-linking of the scaffold,
the fibers were able to direct mineralization of CDHA to form a
biocomposite, in which the crystallographic
HPO
2
4
-axes of the nano-sized
crystals of CDHA were aligned with the long axes of the fibers. This
alignment was similar to that observed between collagen fibrils
and crystals of biological apatite in bones [182]. Other attempts to
fabricate artificial materials having bone-like both nanostructure
and chemical composition were performed and several significant
achievements were obtained [492, 493].
The classical model of biomineralization considers mineral
formation as an amplification process in which individual atoms or
molecules are added to existing nuclei or templates [1, 2, 494]. This
process occurs in the presence of various bioorganic molecules, which
deterministically modify nucleation, growth, and facet stability. A
model involving aggregation-based growth [495] recently challenged
this conventional concept for the crystal growth. Inorganic nano-
sized crystals were found to aggregate into ordered solid phases
c
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