Preparation and Mechanism of Novel Bioceramics with Controllable Morphology and Crystal Growth - Advanced Bioactive Inorganic Materials for Bone Regeneration and Drug Delivery - page 168

QUE is a naturally occurring flavonoid (also belongs to polyphenols) in our
daily food, which has a planar structure and tends to form highly oriented
nanostructures in suspension (Sahoo et al. 2011). The molecular size of QUE
is in a similar dimension to the unit cell formed by Ca 2+ ions on the (1 1 0)
faces (a, b plane) of HAp (Posner and Betts 1975; Dey et al. 2010). The nega-
tive charge of the QUE molecule plane makes it attracted to the positively
charged a, b plane of HAp. Therefore, the specific molecular complementar-
ity between QUE and HAp associated with the negative charge property of
QUE played very important roles in the orientation control of HAp crystal
growth, for they enabled QUE to carry and release Ca 2+ ions and attach to the
HAp surface under the hydrothermal reaction environment with different
QUE concentrations.
6.3 Conclusion and Perspective
Bioactive bioceramics are widely used in hard tissue repair and regeneration,
and also in drug and gene delivery systems. The performance of bioceram-
ics in their applications depends greatly on its crystal morphologies, particle
sizes and size distribution, aggregates, and 3D architectures. Various strate-
gies have been developed to control the morphology and 3D architectures of
the bioceramic materials, and the mechanisms behind them might be very
different. In this chapter, we summarize the preparation and mechanism
of bioceramic materials with controllable morphology and crystal growth.
However, there are still many open questions and challenges within this field
that need to be further investigated in detail. The real mechanisms for the con-
trolling of the morphology and crystal growth need to be comprehensively
researched and confirmed. It is still difficult to synthesize the uniform bioc-
eramic particles with monodispersion and narrow-size distribution in large
scale, which is very important in drug and gene delivery system applications.
The fabrication of bonelike and enamel-like bioceramics with highly oriented
architectures also remains a great challenge. Up to now, few works have been
reported on the fabrication of large size (such as in centimeter size) bioceram-
ics and scaffolds with nano- and microstructured surfaces. It could be con-
cluded that the self-assembly and biomineralization methods are the direction
of the future in the morphology control for bioceramics. Furthermore, more
and arduous works in the study of the relationships and interactions between
the morphologies, grain sizes, crystal aggregations, architectures, and the cell
and tissue biological responses remain to be undertaken.