Biomedical Engineering Reference
In-Depth Information
because of their compositional and partly structural analogy to nat-
ural bone.
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-
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The nano-HA, collagen-based composites can be prepared by
directly mixing the nano-HA and collagen. But the weak interac-
tions between HA and collagen make them a no-cooperation effect
in vivo
for bone defects repair. A recent review by Supova
55
com-
prehensively describes the problem of HA dispersion in polymer
matrices. Another method involves coprecipitation of collagen fib-
rilsandnano-HAspontaneouslyandisapromisingrouteforachiev-
ing the same hierarchical structure in synthetic materials as in
bone. It is also believed that the manufacture using biomimetic self-
assembly of nanocomposite grafts with certain features of natural
bone either compositionally or structurally may replicate the nat-
uralbonegrowthprocess.
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Thismethodwasfirstlyreported
in 1995.
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Collagen is first dispersed in an acidic solution, and then
the coprecipitation is induced by increasing the pH or by the addi-
tion of mixing agents. The direct nucleation of HA nanocrystals
onto collagen fibers has been performed starting from an aque-
oussuspensionofcalciumsolutionandphosphatesolutiontogether
with collagen solution of pH 9-10 at room temperature. A solu-
tion condition of high ion concentration and high pH value was
employed. The obtained composite product was freeze-dried at
40˚C. The nanocrystals of HA elegantly aligned with their c-axis
preferentially oriented along the collagen fibers. As this process
mimics mineralization of natural bone to a certain extent, it is sug-
gested that the HA/collagen nanocomposite can be used for bone
repair and regeneration. Based on the previous research, a manu-
facturing route for assembly of a nano-HA/collagen composite has
beendesignedinourlab.
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Moreover,three-dimensionalscaffolds
have also been prepared with the addition a small amount of a
poly(lactic acid) (PLA) polymer to improve the mechanical proper-
ties of the scaffold.
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These materials are good examples that mimic
natural bone to some extent at the supermolecular structure level.
Their biological evaluation suggests that such bone-resembling
composites are readily incorporated into the bone metabolism in
a way similar to bone remodeling, instead of acting as permanent
implants.
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