Download Artificial Oxygen Carriers

Artificial Oxygen Carriers
The transport of Oxygen to the
muscles and organs of the body is one of
the most vital function performed by the
circulatory system. The lack of oxygen
is a primary cause of death in accidents
and occasionally in illness and surgery.
Blood transfusions have been
used for decades to replace the blood
lost from injury or surgery. The supply
of donors is low and the shelf life of
human blood is only a few weeks. In
addition the blood must be typed
carefully to insure it will not cause
rejection by the victim’s body.
Plasma and other forms of
modified blood can replace the lost
volume of the blood but do not restore
its capacity to transport oxygen. To fill
that need researchers have been trying to
produce artificial chemicals that mimic
the action of red blood cells in the
human body.
Modified Hemoglobin
One solution was to use a
modified form of the chemical used by
our own red blood cells, hemoglobin.
Natural hemoglobin decays within hours
from a tetramer protein into a dimer,
which is useless and highly toxic to the
liver. Researchers have tried to
chemically stabilize hemoglobin or to
encapsulate it within artificial red blood
cells.
All forms of modified
hemoglobin yet produced have an
exceptionally short lifespan in the
human bloodstream – the best
achievement is with artificial red blood
cells that have a half-life of about 20
hours. However, modified hemoglobin is
successful for short-term infusions in
clinical trials.
Perflourochemicals
The other viable option – and the
only one that has been approved for
commercial production and use – is the
perflourochemical. This is a synthetic
organic material made of silicone and
fluorocarbon that, when liquid, can
dissolve a large quantity of O2 and CO2.
Laboratory tests in the 1960’s proved
that mammals could survive by
breathing oxygenated silicon oil or
liquid fluorocarbon and rats have been
shown to survive the total replacement
of their blood for short periods without
ill effect.
However, perflourochemicals
suffered from many of the same
drawbacks as modified hemoglobin –
short survival time and dangerous side
effects. Because they dissolve oxygen
rather than chemically binding, they
must be inserted as liquids inside a semipermeable membrane and most
perflourocarbons have a high rate of
tissue retention.
Oxygent is the only form of
perflourocarbon currently on the market.
It is licensed only for veterinary use and
is undergoing stage III trials in humans.
It is an emulsion of perflourocarbons and
a lecithin membrane. Lecithin is a
chemical already used as a component in
intravenous nutrients and anesthetics.