Preparation and Mechanism of Novel Bioceramics with Controllable Morphology and Crystal Growth - Advanced Bioactive Inorganic Materials for Bone Regeneration and Drug Delivery - page 148

The morphology, structure, and size of bioceramic crystal and aggregates
influence the performance in their applications. For example, rodlike, wire-
like, and sheetlike particles have a stronger molecular adsorption property
due to the increased surface area, whereas rodlike, whiskerlike, wirelike,
and sheetlike inorganics can be used as mechanical reinforcement to fab-
ricate biocomposites because of their excellent mechanical properties. The
nanostructured porous or hollow materials with hierarchical architectures
can be used as a drug or gene delivery system because of their high drug
loading and favorable controllable release properties.
Material with initiative stimulation capacity in tissue regeneration is the
major character for next-generation biomaterials (Hench and Polak 2002).
However, up to now most of the bioceramics, including the traditional
Ca-P-based bioceramics, lack the ability to stimulate the formation of new
bone, which hindered their clinical applications (Tabrizi et al. 2009). Several
attempts have been made to solve this problem, such as loading bioactive
growth factors (Notodihardjo et al. 2012), surface morphology and topology
design (Wong et al. 1995; Kuboki et al. 1998; Ribeiro et al. 2010), and the incor-
poration of the functional trace elements (Lin, Chang, Liu, et al. 2011; Lin,
Zhou, et al. 2011). Recently, the improvement of the biological responses via
surface morphology and topology design has aroused great interest.
Various strategies have been developed to fabricate bioceramic materials
with different morphologies, such as platelike (or sheetlike); needles, rods,
whiskers, and fibers; mesostructures; spheres; core-shell structures; and
three-dimensional (3D) hierarchical architectures from nano- to microscales.
The most common methods to control the morphologies are based on the
template-directing strategy. The templates could be “soft materials,” such as
surfactants, polymers, and biomoleculars, or “hard materials,” such as cal-
cium carbonates, calcium phosphate, and calcium silicates. The mechanisms
behind the template-directing processes are different. Another interesting
strategy of morphology control is the self-assembly without using any tem-
plates, such as mineralization, which are known as wet chemical routes.
In this chapter, the recent developments of the preparation and mechanism
of novel bioceramics with controllable morphologies are summarized. Due
to the limitation on length, most examples focus on Ca-P-based materials.
6.2 Preparation and Mechanism of Novel Bioceramics with
Controllable Morphologies and Crystal Growth
6.2.1 Crystal Growth and Morphology Control of Bioceramic Particles
Many methods have been applied to synthesize bioceramic particles with
different morphologies, crystal sizes, and chemical components. These