Biomedical Engineering Reference
In-Depth Information
surface area, particle size, and morphology of nanodimensional
apatites.
In some cases, special polymers can be used as spatial reaction
vessels for fabrication of CDHA. For example, Shchukin et al.
employed
4
3-
a poly (allylamine hydrochloride) / PO
complex as a source of
orthophosphate anions to capture calcium cations and make them
react in the capsule volume [430]. Bose and Saha synthesized
spherical-like nanocrystalline CDHA powder with particle diameters
of ~30 and ~50 nm using the emulsion route [365]. Furthermore,
nano-sized crystals of apatite might be aggregated into microspheres
[376, 431]. Hexadecyl (cetyl) trimethylammonium bromide (CTAB)
was selected as an efficient agent to modulate the formation of
CDHA nano-sized particles [428, 432]. The particle size can be
regulated feasibly by changing the concentration of CTAB in the
supersaturated by calcium orthophosphates solutions. For example,
three different types of spherical particles of nano-sized CDHA with
average diameters of 20 ± 5, 40 ± 10, and 80 ± 12 nm were fabricated
using a series of CTAB concentrations to control the particle size. The
experimental results revealed that the dimensions of the prepared
nano-sized CDHA were relatively uniform. In contrast, nano-sized
CDHA grown in the absence of organic additives are typical, rod-like
particles with lengths of hundreds of nanometers and width of tens
of nanometers [432].
To conclude this part, the surface of nano-sized particles of
apatite might be functionalized by various compounds (even by
quantum dots [433, 434]) to provide new important properties
[422, 435-440], e.g
fluorescence [27-29, 439] and luminescence
[434, 440]. Both fluorescence and luminescence can be used as a
tracking property for the nano-sized particles to give an observable
indication of agent delivery, while the particles are served to protect
the agent
.
,
in vivo
until it has reached the destination.
3.6.3
Nanodimensional and Nanocrystalline TCP
Many researchers have formulated synthesis of nanodimensional
β-TCP. For example, Bow et al.
synthesized β-TCP powders of ~50 nm
particle diameter at room temperature in anhydrous methanol as a
solvent [441]. With increase in aging time, the phase transformation
was found to take place from initial DCPA, to intermediate ACP
phases, then to final β-TCP. The authors observed that incorporation
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