Biomedical Engineering Reference
In-Depth Information
intopatternsorstructureswithouthumanintervention.Itisconsid-
ered that self-assembling processes are common throughout nature
and technology. Therefore we begin this paper with a discussion
about the components and hierarchical structure in natural bone
tissue by self-assembling and then give a description of work on
biomemiticfabricationofbonetissueengineeringscaffoldmaterials
using self-assembled collagen mineralization. Finally, we finish by
reviewingthecurrentapplicationsanddevelopmentofsuchscaffold
materials.
37.2 Compositional and Structural Characteristics of
Natural Bone
To produce an excellent bone substitute material, it is necessary to
emphasize several compositional and structural characteristics of
natural bone.
37.2.1
Composition of the Natural Bone Matrix
Bone is a complex tissue that is composed of some organic matrices
uponwhichHAcrystalsaredeposited.Ninetypercentoftheorganic
materials in the bone matrix are collagen I, with the remaining ten
percentconsistingofvariousglycoproteinsandproteoglycans.Inter-
spersedthroughouttheorganicmatrixarecrystalsofHA,whichgive
the bonematrix its stiffness.
12
37.2.2
Hierarchical Structure of the Natural Bone Matrix
by Self-Assembly
Landis has put forward the microstructure model of the bone
matrix, which is generally accepted.
13
According to the model, the
interactions between the collagen molecules result in the charac-
teristic quarter repeat of 67 nm and in a complex cross-striation
banding,whichresultsinassemblyofthecollagentriplehelicesinto
microfibrils, forming the supramolecular structures.
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16
The pack-
ing of collagen molecules is that five tropocollagen molecules align
longitudinally with an overlap of approximately a quarter of the
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