Biomedical Engineering Reference
In-Depth Information
a calcium orthophosphate cement with an exogenous nerve growth
factor [559]. Even more complicated combination of deproteinized
osteoarticular allografts integrated with a calcium orthophosphate
cement and recombinant human vascular endothelial cell growth
factor plus recombinant human BMP-2 (rhBMP-2) has been studied
as well [560]. Interestingly, but the drug delivery properties of
calcium orthophosphate cements might be influenced by crystal
morphology [561].
In the cement formulations, drugs might be incorporated into
both a liquid and a powder phases. After setting, the drugs are
slowly released through the cement pores [210, 543-546, 562, 563].
For example, a group of investigators added flomoxef sodium to a
cement formulation and found that the release of antibiotic could be
easily controlled
in vivo
by adjusting the content of sodium alginate
elution of vancomycin from calcium
orthophosphate cement has been studied as well [563]. The possibility
of using self-setting calcium orthophosphate formulations as a drug-
delivery system offers an attractive and efficient solution for the
treatment of various bone diseases, e.g.,
in the formula [210].
In vitro
tumours, osteoporosis and
osteomyelitis, which normally require long and painful therapies.
The laboratory studies on drugs incorporation into self-setting
calcium orthophosphate formulations cover different aspects. Firstly,
it is necessary to verify that addition of a drug does not influence
the setting reaction not only in terms of the setting and hardening
mechanisms but also with respect to the rheological behavior and
injectability. Secondly, it is necessary to determine the
in vitro
kinetics of drug release. Thirdly, the drug delivery properties of the
formulation must be studied
. Finally, but still importantly, the
clinical performance of the drug delivery system must be evaluated
as well [36, 37]. For example, recombinant human transforming
growth factor β1 (rhTGF-β1) was added to a calcium orthophosphate
cement [564-567]. This resulted in formation of a bioactivated
cement that could be used as a bone filler and for the replacement
of bone [564]. It appeared that after 8 weeks the addition of growth
factors stimulated and increased bone formation (50% volume) and
bone contact (65%) in comparison to control calvarian defects in an
animal study. Besides, the growth factor group reduced the remaining
volume of the cement by 20% [565]. Examples of rhBMP-2 release
from a loaded porous calcium orthophosphate cement might be
in vivo
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