integration of these architectures into functioning devices for anticipated electrical,
optical, magnetic, and chemical outputs. Only with an appreciation and understanding of the principles of calcium phosphate mineralization in such biosystems can
such proposals be achieved.
Collagens comprise a family of extracellular matrix molecules responsible for
the integrity and mechanical properties of both soft and hard connective tissues,
including cornea, skin, tendon, cartilage, and bone. Almost all of the connective
tissues with collagen fibrils as the basic building blocks have remarkably similar
chemistry at the macromolecular and fibrillar levels of structure. However, differentiation in the hierarchical structure takes place as these fibrils are arranged in the
specific architecture required from the construction of special tissues each with
unique functions.
Here it focuses principally on the self-assembly of mineralized collagen
composites in hard connective tissues and on the relative involvement of mimetic
insoluble organic structures in controlled mineralization. In most cases of such
mineralization where collagen fibrils are involved, the matrix is a polymeric
framework that consists of a complex assembly of macromolecules. Natural bone
is a representative example with a typical hierarchically ordered organization. Bone
tissues are mainly constructed from nano-sized hydroxyapatite crystals and a
collagen framework in which the crystals form, resulting in a highly complex but
ordered mineral–organic composite material. This composite itself is organized into
layers or lamellae, each with the thickness of a few microns, and in turn these are
arranged into higher order structures in a variety of ways depending on the specific
bone types (Cui et al. 2007).
6.5.1 Collagen-Induced Calcium Phosphate Mineralization
The hierarchical structure of bone formed by assembly of an orderly deposition of
HA minerals within the type I collagen matrix. The crystallographic c-axis of the
crystals is oriented preferentially parallel along the longitudinal axis of the collagen
fibrils. Both investigations and simulations of the hierarchical nanofibril structure in
naturally occurring materials can offer some new ideas in the design and fabrication
of new functional materials, such as tissue engineering scaffolds and biomimetic
engineering materials. Scientists have attempted to mimic the collagen-mineralization
process in vitro in order to achieve a better understanding of the organizational
structure in naturally occurring tissues in which the major organic matrix is collagen.
Numerous studies about mineralized collagen have been reported.
By combining the collagen fibril assembly and the calcium phosphate formation
in one process, Bradt et al. (1999) obtained a homogeneously mineralized collagen
gel, consisting of a three-dimensional network of collagen fibrils covered with
calcium phosphate. The initial precipitate, along with the fibril assembly, was
amorphous calcium phosphate. This was then transformed into a crystalline apatite-like phase. The addition of polyaspartate to the reaction mixture was found to
188
Q. Feng
optical, magnetic, and chemical outputs. Only with an appreciation and understanding of the principles of calcium phosphate mineralization in such biosystems can
such proposals be achieved.
Collagens comprise a family of extracellular matrix molecules responsible for
the integrity and mechanical properties of both soft and hard connective tissues,
including cornea, skin, tendon, cartilage, and bone. Almost all of the connective
tissues with collagen fibrils as the basic building blocks have remarkably similar
chemistry at the macromolecular and fibrillar levels of structure. However, differentiation in the hierarchical structure takes place as these fibrils are arranged in the
specific architecture required from the construction of special tissues each with
unique functions.
Here it focuses principally on the self-assembly of mineralized collagen
composites in hard connective tissues and on the relative involvement of mimetic
insoluble organic structures in controlled mineralization. In most cases of such
mineralization where collagen fibrils are involved, the matrix is a polymeric
framework that consists of a complex assembly of macromolecules. Natural bone
is a representative example with a typical hierarchically ordered organization. Bone
tissues are mainly constructed from nano-sized hydroxyapatite crystals and a
collagen framework in which the crystals form, resulting in a highly complex but
ordered mineral–organic composite material. This composite itself is organized into
layers or lamellae, each with the thickness of a few microns, and in turn these are
arranged into higher order structures in a variety of ways depending on the specific
bone types (Cui et al. 2007).
6.5.1 Collagen-Induced Calcium Phosphate Mineralization
The hierarchical structure of bone formed by assembly of an orderly deposition of
HA minerals within the type I collagen matrix. The crystallographic c-axis of the
crystals is oriented preferentially parallel along the longitudinal axis of the collagen
fibrils. Both investigations and simulations of the hierarchical nanofibril structure in
naturally occurring materials can offer some new ideas in the design and fabrication
of new functional materials, such as tissue engineering scaffolds and biomimetic
engineering materials. Scientists have attempted to mimic the collagen-mineralization
process in vitro in order to achieve a better understanding of the organizational
structure in naturally occurring tissues in which the major organic matrix is collagen.
Numerous studies about mineralized collagen have been reported.
By combining the collagen fibril assembly and the calcium phosphate formation
in one process, Bradt et al. (1999) obtained a homogeneously mineralized collagen
gel, consisting of a three-dimensional network of collagen fibrils covered with
calcium phosphate. The initial precipitate, along with the fibril assembly, was
amorphous calcium phosphate. This was then transformed into a crystalline apatite-like phase. The addition of polyaspartate to the reaction mixture was found to
188
Q. Feng