Biomimetic Synthesis of Self-Assembled Mineralized Collagen-Based Composites for Bone Tissue Engineering - Biomimetics: Advancing Nanobiomaterials and Tissue Engineering - page 39

HA and silk fi broin are both excellent materials in biomaterials areas.
HA has outstanding osteo-conductivity and bioactivity, and silk fi broin
is also an extensively used biomaterial. The fi broin-HA nanocomposites
have a good prospect to be explored as bone repair materials.
The structure, character and amino acid sequence of RHLC, silk fi broin
and natural collagen are different [71]. The mineralization of RHLC and
silk fi broin confi rmed the proposed mechanism on the self-assembly of
mineralized collagen fi brils introduced in Section 2.3.1. It is reasonable to
speculate that most proteins could regulate calcium phosphate deposition
during mineralization in vitro . As well as proteins, polypeptides also can
be used in regulating mineralization [53]. With the help of gene technol-
ogy, the recombinant proteins or polypeptides can be designed according
to different demands, and therefore have various applications in bone tis-
sue engineering.
2.3.4 In Vitro Self-Assembly of Mineralized
Peptide-Amphiphilic Nanofi bers
One of the great challenges for materials science is the creation of supramo-
lecular materials in which the constituent units are highly regular molec-
ular nanostructures. Fabrication of materials that resemble bone is very
diffi cult because it involves two dissimilar organic and inorganic nano-
phases, each of which have a specifi c spatial relation with respect to each
another. One way to accomplish this in an artifi cial system is to prepare an
organic nanophase designed to exert control over crystal nucleation and
growth of the inorganic component [53]. Studies on such template crystal
growth methods have suggested that nucleation occurs on surfaces which
expose repetitive patterns of anionic groups. These anionic groups tend
to concentrate the inorganic cations creating a local supersaturation fol-
lowed by oriented nucleation of the inorganic crystal phase. At present
there is an increasing interest in the fabrication of HA/peptide composites
using designed self-assembling systems.
Many groups have investigated the preparation of bone-like materials.
Stupp et al . have reported several studies on the use of self-assembly and
mineralization to prepare a nanostructured composite material that recre-
ates the structural orientation between collagen and HA observed in bone
[73-75]. The composite is prepared by self-assembly, covalent capture, and
mineralization of a peptide-amphiphile (PA) which is synthesized by stan-
dard solid-phase chemistry ending with alkylation of the Nterminus of the
peptide. Chemical structure of the peptide amphiphile molecule consists
of fi ve key structural features [53]. Region 1 is a long alkyl tail that conveys
hydrophobic character to the molecule and, when combined with the pep-
tide region, makes the molecule amphiphilic. Region 2 is composed of four
consecutive cysteine residues that may form disulfi de bonds with other