Biomedical Engineering Reference
In-Depth Information
al., [902] and occasionally named as Kokubo's SBF. It is a metastable
aqueous solution with pH ~7.40, supersaturated with respect to
the precipitation of OCP, β-TCP, CDHA and HA [903], containing
only inorganic ions in concentrations nearly equal to those in
human blood plasma. However, the standard SBF formulation,
firstly, contains the tris/HCl buffer, and, secondly, the concentration
of hydrogencarbonate (4.2 mM) is only a fraction of that in blood
plasma (27 mm) [902]. The problem of a low concentration of
hydrogencarbonate ions has been overcome by first introducing
a “synthetic body fluid” [904-906] and later a revised SBF (rSBF)
[907, 908]. Due to the chemical similarity with human blood plasma,
rSBF currently seems to be the best simulating solution. However,
it contains Hepes buffer, loses CO
in open vessels and does not
contain any organic and/or biological molecules [907, 908]. Other
types of SBF are also available [909-912] and the interested readers
are referred to a leading opinion co-authored by the SBF inventor
[913], where the entire history and the preparation techniques of
various SBF formulations are well described. recently, another
leading opinion on the suitability of SBF for the
2
bioactivity
tests was published [914]. The authors demonstrated that (i) there
is presently no enough scientific data to support the SBF suitability
and (ii) even though bioactivity tests with SBFs are valid, the way the
tests are generally conducted leaves room for further improvements.
Furthermore, the preparation protocol of SBF solutions was
reconsidered and a new procedure was suggested to improve
the reproducibility of bioactivity tests [914]. The application of
SBF for the surface mineralization of various materials
in vitro
in vitro
has been reviewed in Ref. [915], while the theoretical analysis of
calcium orthophosphate precipitation (the driving force and the
nucleation rate based on the classical crystallization theory) in
SBF is also available [903]. It is important to note that nanometer-
sized prenucleation clusters in SBF solutions have been discovered
[850]; those clusters are believed to be the initial building blocks of
crystallized calcium orthophosphates (e.g., CDHA [291]), while the
crystallization process itself occurs via intermediate formation of
ACP (Fig. 1.17).
Further attempts to improve the biomimetic properties of SBF and
rSBF have been performed [913, 914]. Efforts were made to replace
artificial buffers (tris/HCl, Hepes) with simultaneous increasing the
concentration of hydrogencarbonates for SBF [916-918] or avoiding
Search WWH ::
Custom Search