Biomimetic Synthesis of Self-Assembled Mineralized Collagen-Based Composites for Bone Tissue Engineering - Biomimetics: Advancing Nanobiomaterials and Tissue Engineering - page 40

cysteines on neighboring PA peptides to polymerize the self-assembled
structure. Region 3 is a fl exible linker region of three glycine residues to
provide the hydrophilic head group fl exibility from the more rigid cross-
linked region. Region 4 is a single phosphorylated serine residue that is
designed to interact strongly with calcium ions and help direct miner-
alization of hydroxyapatite. Region 5 displays the cell adhesion ligand
Arg-Gly-Asp (RGD). This peptide-amphiphile assembles into nanofi -
bers, which are stable in alkaline solutions. Moreover, high-resolution
TEM (HRTEM) observations have shown a donut-shaped pattern in the
cross section of the fi bers, indicating that the hydrophobic alkyl tails pack
inside of the fi ber micelle and leave the acidic moieties of the peptide
exposed to the aqueous environment. The chemistry of the peptide region
is thus repetitively displayed on the surface. HA are nucleated on the sur-
faces of the fi bers. The orientation of the crystalline nuclei and the subse-
quent crystal growth are not random but are controlled by the micelles.
Molecular self-assembly is a powerful approach for the synthesis of
novel supramolecular architectures. Zhang et al. have focused on the fab-
rication of several self-assembling peptides and proteins for a variety of
studies of biomaterials [76]. Their studies have shown that a broad range
of peptides and proteins have the ability to produce very stable nanofi bers
[77]. And these nanofi bers are similar in scale to the extracellular matrices
that are crucial in manufacturing artifi cial functional tissues.

2.4 Applications of Mineralized Collagen-based

Composites for Bone Regeneration

2.4.1 Fabrication of Nano-HA/Collagen-based Composites

2.4.1.1 Three-Dimensional Biomimetic Bone Scaffolds: Nano-HA/

Collagen/PLA Composite (nHAC/PLA)

The gold standard for the treatment of large bone defects and nonunions is
autologous bone grafting. However, the supply of autograft is limited and
donor site morbidity is also a concern along with the required prolonged
operation times [2]. The alternative of allogeneic bone has potential risks
of disease transmission and infection [3]. In order to avoid the problems
associated with either autologous or allogeneic bone grafts, there has been
a continued interest in the use of synthetic bone graft materials during the
past decades.
Bone tissue engineering is a promising method for the repair of large
bone defects [78]. The ideal bone scaffold should promote early mineral-
ization and support new bone formation, while at the same time allow-
ing for replacement by new bone. Recently, a highly porous scaffold is