Biomimetic Synthesis of Self-Assembled Mineralized Collagen-Based Composites for Bone Tissue Engineering - Biomimetics: Advancing Nanobiomaterials and Tissue Engineering - page 42

The nHAC/CSH cement is fabricated by introducing CSH into nHAC.
It is a new bone substitute with satisfactory biocompatibility, which can
offer a satisfactory biological environment for growing new bone in the
implants and to stimulate bone formation. The composite cement also
may support the growth of blood vessels and osteogenic cells [92]. It can
act not only as a void fi ller facilitating guided tissue regeneration, but
also as an accelerator for the healing process [93]. Compared with others,
nHAC/CSH is a promising material for bone tissue engineering in the
clinical repair of large or irregular bony defects.

2.4.2 Functional Improvements of Mineralized Collagen-based

Composites

New generation tissue-engineered scaffolds are bioactive and biodegrad-
able simultaneously, and are capable of recruiting, programming and sim-
ulating host cells with specifi c cellular responses at the molecular level for
in situ tissue regeneration. Bioactive molecules such as growth factors and
cytokines have been loaded into biomaterial scaffolds to regulate cellular
growth and related functions in a better way [94].
Growth factors can be effectively delivered to a bone defect through
nanocomposites, and the in vivo effi cacies of such methods should be
evaluated exactly [86]. Bone morphogenetic protein-2 (BMP-2) is the most
powerful member of BMP family in inducing bone formation [95, 96].
Recombinant human BMP-2 (rhBMP-2) has already been clinically applied
to induce bone regeneration in both fracture healing and spinal fusion. The
in vivo performance of the nanocomposite for bone repairing with rhBMP-2
has been proven better than that of the nanocomposite without rhBMP-2.
Platelet-rich plasma (PRP) has already been used for bone regeneration
when combined with bone scaffolds. The rationale for the local applica-
tion of PRP in bone tissue engineering is based on the autologous release
of growth factors [97-99] (platelet-derived growth factor, transform-
ing growth factor- , insulin-like growth factor, and vascular endothelial
growth factor) present in the platelets without the risk of disease transmis-
sion or immunogenic reactions. PRP is absorbed into the scaffold mate-
rial while under vacuum during fabrication by the collagen of nHAC/
PLA. After implantation, platelets and their growth factors act in the ear-
lier stage of the bone regenerative process due to the short life span of
platelets. Therefore, the direct effects of growth factors only last 5-7 days
if no controlled release material is involved [100]. After the initial burst of
growth factors, the platelets synthesize and secrete additional growth fac-
tors for the remaining days of their life span to stimulate the proliferation
and differentiation of stem cells at the defect site [101].
Rapid angiogenesis in tissue-engineered scaffolds has been thought
to be a critical element determining the success of the transplantation,