Strategy for a Biomimetic Paradigm in Dental and Craniofacial Tissue Engineering - Biomimetics: Advancing Nanobiomaterials and Tissue Engineering - page 136

Recent advances in nanotechnology have enabled the design and
fabrication of nanoscale ECM-analog materials [105, 106]. To maintain
tissue-specifi c architecture and function, the ECMs of various tissues in the
craniofacial complex differ in their chemical composition and spatial orga-
nization of the collagens, elastins, proteoglycans and adhesion molecules,
and in their mechano-physical properties that engage micro-environmental
sensing or mechanotransduction of the cells. Mechanotransduction is
the regulation of cellular function by environmental mechanical cues.
Mechanical stress and strain in vivo are the key regulatory mechanical
cues that guide cell morphogenesis and affect the healthy maintenance of
tissues [107]. To design tissue-specifi c scaffolds, the recapitulation of the
surface chemical and mechanical properties on the nanoscale is a crucial
factor that functional tissue engineering cannot afford to overlook.

6.5.3 Nanotechnology for Engineering Craniofacial

Mineralized Collagenous Structures

Bone is a complex structure of mineralized collagen fi brils forming the basic
building blocks of mineralized hard tissues. The regulation of the intrafi -
brillar mineralization process takes place through interactions between
the collagen matrix, the noncollagenous extracellular proteins and the
hard inorganic components composed of nanocrystalline hydroxyapatite
(HA) (20-80nm long and 2-5nm thick) [108]. During bone regeneration,
the HA serves as a chelating agent for mineralization of osteoblasts while
the collagen provides mechanical support, promoting adhesion and pro-
liferation [94]. It is such a peculiar structure that, when mirrored on the
nanolevel, would achieve the desirable osteoconductivity and mechanical
properties that ought to characterize a bone engineering scaffold.
At present, nanotechnology has been fi ne-tuning the emulation of the
collagenous organic and/or the HA mineral phases of bone to achieve
the osteoconductivity and mechanical properties [109, 110]. The synthesis
of scaffolds with a pattern of highly mineralized collagen fi brils identi-
cal to those of natural bone, with nanoapatite crystallites preferentially
aligned along the collagen fi bril axes, have already demonstrated a boost
in bone regeneration [109]. The HA nanoparticles incorporated within a
bone engineering scaffold have demonstrated enhancement in compres-
sive mechanical properties and stiffness as well as improvement of the
in vitro bioactivity of the construct [111], while the apatite nanostructure
on the surface of HA particles can be designed as a biomimetic surface to
promote osteogenic differentiation [112].
To deal with the limitations of calcium phosphate and polymeric scaf-
folds, nanoparticles-based bone TE technologies have been introduced.
For instance, the introduction of nanoparticle-composite scaffolds demon-
strated increase in mechanical strength for bone grafts, the development