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Chemical Technology • July 2015
huge immune response. And kill you. So you really do want
the right blood for you.
All-in-all, there are 342 different blood-group antigens, of
which 160 are defined as ‘high prevalence’. If you’re lucky,
you’re in that group and you’ll be able to get a transfusion
in an emergency. If you’re not … let’s just say, you don’t
want to be in that group.
There are, for example, only 43 people in the world with
Rhesus null blood. They have no Rhesus antigens. This
makes their blood heart-breakingly precious since they can
donate to anyone who falls into the rare Rhesus blood type
groups. Donated blood is, literally, a life-saver. And, once
donated, it lasts only 42 days. Given this, and the difficulty
of safely storing and distributing blood to those in need, it
is no surprise that the pharmaceuticals industry has been
looking for suitable alternatives.
Artificial blood
The requirements for any artificial oxygen-carrying blood
are many and various. Firstly, it must be compatible with all
blood-types, ensuring it can be used by anyone. It must be
able to transport oxygen at least as efficiently as does blood;
and that is both in terms of its capacity to absorb oxygen,
and to release it once it gets to its destination. It must last
about 120 days once it is transfused to ensure that its rate
of decay matches your body’s rate of production (otherwise
it’s like having a continuous bleed and requires a just as
continuous top-up). And, if that isn’t enough, it must have
similar properties to blood since your body control systems
are designed to deal with specific homeostatic pressures
and flow-rates.
Blood doesn’t only carry oxygen. It acts to clot at sites
of injury to aid healing. It regulates body temperature and
pH, as well as delivering antibodies and white blood cells
to infection.
There are currently two main approaches to developing
artificial blood. The first is to use haemoglobin (Hb), the
molecule in blood which does the job in the first place.
Given that red blood can only be stored for 42 days, a vast
amount of blood is discarded. One can have a shortage
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