Biomedical Engineering Reference
In-Depth Information
biphasic (HA + β-TCP) bioceramics was successfully prepared by
microwave synthesis [455, 456] and a polymer matrix mediated
process [457] in other studies. Good cellular activities of the biphasic
bioceramics have been reported.
Layrolle and Lebugle developed a synthesis route of nano-sized
FA and other calcium orthophosphates, using calcium diethoxide
(Ca(OEt)
F to prepare FA [458]) as the
initial reagents and anhydrous ethanol as a solvent. By a simple
variance of the ratio of reagents, calcium orthophosphates of
various chemical compositions were precipitated in ethanol. The
precipitates were characterized and the results indicated that those
calcium orthophosphates were amorphous and nanodimensional.
Furthermore, they had large specific surface areas and possessed a
high reactivity [129, 458].
) and H
PO
[129] (+ NH
2
3
4
4
3.6.4
Other Nanodimensional and Nanocrystalline
Calcium Orthophosphates
Nano-sized particles of DCPD (with some amount of CDHA and
ACP) of a relatively high monodispersity could be synthesized from
aqueous solutions of calcium nitrate and H
in the presence of
2-carboxyethylphosphonic acid. They are produced in a discoid
shape with a diameter of 30-80 nm and a height of less than
~5 nm. They form stable colloidal solutions displaying minimal
agglomeration [459]. Nano-sized rods and nanodimensional fibers
of DCPD with average diameters of 25 ± 5 nm (aspect ratio ~6)
and 76 ± 20 nm (aspect ratio ~40), respectively, were synthesized
by sucrose ester based reverse microemulsion technique [460]. A
similar approach was used in another study [371]. Nanodimensional
crystals of both DCPD and DCPA were prepared by EDTA-assisted
hydrothermal method [311]. An interesting approach comprises
precipitation of calcium orthophosphates inside nano-sized pores
of another material. For example, nanodimensional clusters DCPD
were immobilized into pores of an oxide network by immersion
of this network into an acidic (pH = 2.7) calcium orthophosphate
solution at 50°C [461]. The acid-base reaction between the calcium
orthophosphate solution and the hydroxyl groups of the oxide
network resulted in formation of nanodimensional clusters of
DCPD immobilized inside the oxide pores. Interestingly, but the
immobilized nanodimensional clusters of DCPD were further
PO
3
4
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