Biomedical Engineering Reference
In-Depth Information
that determined the influence of PSS on the crystal growth mode. The flex-
ible polymer with functional groups, such as polyethylene glycol (PEG), can
be also used as the cosurfactant or cotemplate to modulate the morphology
and architecture of the products (Salarian et al. 2009). Spoerke et al. (2009)
designed a scaffolding framework assembled from the peptide amphiphile
(PA) nanofiber, which was mimetic to the natural collagen. The research
shown that enzymatically mediated harvesting of phosphate ions combined
with nanofiber surface nucleation could lead to a spatially selective and bio-
mimetic mineralization in a 3D environment. Their study suggests that both
spatial and temporal elements are necessary to achieve biomimetic mineral-
ization in synthetic materials.
The solution mediated deposition method was also used to fabricate the
inorganic materials. Schmidt et al. (2004; Schmidt and Ostafin 2002) coated
apatite on lipsome micelles to form nanoshells, and the thickness of shells
could be well controlled by adjusting the addition time of calcium and phos-
phate salt. Similarly, Tjandra et al. (2006) directly precipitated apatite on
block copolymer templates, and hollow apatite nanospheres were obtained
after calcination. Fujii et al. (2009) fabricated HAp-coated micrometer-sized
poly(L-lactic acid) (PLLA) microspheres via a “Pickering-type” emulsion
route in the absence of any molecular surfactants. In their strategy, the stable
oil-in-water emulsions were prepared using 40 nm HAp nanoparticles as
a particulate emulsifier and a dichloromethane (CH 2 Cl 2 ) solution of PLLA
as an oil phase, in which the interaction between carbonyl/carboxylic acid
groups of PLLA and the HAp nanoparticles at the CH 2 Cl 2 -water interface
played a crucial role to prepare the stable Pickering-type emulsion. After
evaporation of CH 2 Cl 2 from the emulsion, the HAp nanoparticle-coated
PLLA microspheres were fabricated.
Recently, morphology control of bioinorganic materials through biomi-
metic approaches is one of the most interesting issues in the material fabrica-
tion and application fields, in which the inorganic materials with complex
morphologies can be fabricated. Fowler et al. (2005) synthesized enamel-
like HAp with bundle structures directly from a solution containing AOT,
water, and oil. The bundles were only 750 nm to 1 mm in length and 250 to
350 nm in width. In biological bone, the composite structure of nanosized
HAp reinforced collagen offers a route to manufacture materials with high
strength and high toughness. The micrometer spherical HAp crystals with
the diameter of 1 to 3 µm were synthesized via a biomimetic process using
1.5% β-cyclodextrin (β-CD) as a template (Xiao et al. 2009). The interaction
between Ca 2+ ions and function groups -OH in β-CD reduced the drifting
velocity and the concentration of ions, which resulted in the decrease of elec-
trical conductivity. This interaction between Ca 2+ and β-CD is possibly one
of the influence factors on the nucleation and growth of the spherical HAp
crystal. In addition, β-CD is a cyclic oligosaccharide consisting of seven α-(1-
4)-linked D-glucose units. This special molecular structure provides a mol-
ecule shaped like a segment of a hollow cone with an exterior hydrophilic
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