Biomedical Engineering Reference
In-Depth Information
elegantsystem,theactivationmechanismisdesignedtobeusedasa
switchincontrollingtheoxygenreleasetimeandrate.Suchstepsare
veryimportanttoensurethecorrectdosageandratearesuppliedto
the targeted applications. Finally, a proper storage method should
be considered for the microspheres that are not being used imme-
diately to avoid loss of oxygen. One good option will be the direct
freezing of microspheres under a super-low temperature using liq-
uidnitrogentoreducethereleaserateoftheoxygensource.Besides,
the direct incorporation into other formats such as scaffolds to be
used immediately isanother option to replace the storage process.
Having the understanding of the state of the art for the develop-
ment of ORMs, an attempt has been made to produce ORMs using
hydrogen peroxide (H
2
O
2
) as an oxygen source that is encapsu-
lated within a biodegradable matrix. The main concept behind the
system is the production of oxygen upon the chemical decompo-
sition of H
2
O
2
that is released from the core of the microspheres.
Encapsulation stabilizes H
2
O
2
and induces a controlled release for
prolonged generation of oxygen in sustaining optimum cell sur-
vival. In contrast, the direct usage of free H
2
O
2
generates oxygen
in high level of concentration at once and can cause a serious toxic
effect to cells instead of facilitating their survival.
46
The use of
H
2
O
2
was based on several considerations besides its well-known
chemistry.
47
The decomposition process of H
2
O
2
is rather simple,
consisting of a single-step reaction, and produces only oxygen and
waterasby-products.Thiseliminatesthepossibilityofhavingharm-
ful by-products generated from the chemical reaction. Even the by-
products produced may not be toxic, such as metal cations in some
cases, but accumulation can increase the concentration, leading to a
high possibility of an interfering effect towards the biological sys-
tem. Besides, H
2
O
2
is commercially available, easy to obtain, and
considerably economical. However, there are also some drawbacks
in using H
2
O
2
, which you need to be aware of and improve to avoid
failure in producing ORMs for biological applications. H
2
O
2
decom-
poses easily under normal conditions and requires extra precaution
toavoidexcesslossduringthehandling.Besides,H
2
O
2
isharmfulto
cells when in direct contact and is often used as an antiseptic to kill
bacteria.
48
Therefore, assurance is required that only oxygen mole-
cules reach the cells during the tissue reconstruction process but
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