Biomedical Engineering Reference
In-Depth Information
to overcome this limitation over the years, which include the use
of artificial oxygen carriers, enhancement and speeding up of the
vascularization in tissues, and the attempts at fabricating oxygen-
generating biomaterials. All these efforts have improved the sup-
ply e
ciency of oxygen within the engineering system but to some
extent have not fully succeeded in achieving survival of a clinically
applicable large tissue mass. This section gives some overview of
and insightinto these efforts.
32.2.1
The Use of Artificial Oxygen Carriers
Innature,thesupplyofoxygentocellsisaccomplishedusingthecir-
culation of blood as a carrier. Hemoglobin (Hb) is the component in
blood that is responsible for the role of binding oxygen at the lung,
delivering it, and releasing it to cells over the entire body for the
respiratoryprocess.Themechanismsinvolvedhavebeenintensively
investigatedbyresearchersandwelldocumented.
23
,
24
Nevertheless,
the development of such a system is still currently impossible due
to innovation and technology limitations. However, it has inspired
tenacious and successful efforts in mimicking such a system, espe-
cially in developing novel liquid artificial oxygen carriers based on
synthetic Hb and perfluorocarbons (PFCs).
Cell-free Hb itself tends to dissociate into its individual
αβ
dimmer-dimmer that are rapidly eliminated from the circula-
tory system and reduces the effective lifetime besides causing
kidney damage. In addition, cell-free Hb lacks its essential 2,3-
diphosphoglycerate (2,3-DPG) affector, preventing the release of
oxygen to the tissues.
25
Therefore, modifications are made to
increase the stability besides optimizing its performance towards
the delivery of oxygen. Modifications can be made via direct cross-
linking between Hb, known as the acelullar type, or the encapsu-
lation of Hb into a secondary matrix, known as the cellular type.
26
The Hb-modified carriers have been studied to oxygenate tissues
in overcoming the problem of stroke, sickle cell crisis, and cardiac
arrest.
27
Besides,thepotentialsarealsobeingexploredtobeusedin
overcomingmajorsurgicalbleeding,hemorrhagicshock,andclinical
e
cacy in bloodsparing.
28
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