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Vampires may soon have reason for celebration as an artificial replacement for human blood makes its way into the market. We take a look at the current developments in the field, as we celebrate World Blood Donour Day (June 14) to highlight the need for safe blood.
IN the vampire-themed Twilight saga, a bunch of human-friendly vampires subsist on animal blood rather than people, so they could consume their unnatural diet in a civilised fashion.
Though considered an anaemic alternative next to a bodacious serving of human blood, this “vegetarian” option has allowed some benignant bloodsuckers such as the Cullen clan to co-exist peacefully with humankind.
However, many vampires who have gone vegetarian find it difficult, as human blood gives them more strength. At times, the allure of feasting on a tasty human can also be too strong to resist.
As one sparkly Cullen puts it, subsisting on animal blood is akin to some humans living on tofu. “It keeps you strong, but you’re never fully satisfied.”
In real life, the urge to find a viable substitute for human blood is equally palpable. In fact, the quest to create artificial blood is big business, with over US$1bil (RM3bil) already spent over the last 20 years in various attempts to create a true alternative to blood.
Development of the first blood substitutes dates all the way back to the 1600s, when English physician William Harvey first described how blood was pumped throughout the body by the heart.
In the years that followed, medical practitioners would experiment with substances of sorts, including beer, urine, milk, plant resins and sheep blood as a substitute for blood.
Some even hoped that changing a person’s blood would yield other beneficial effects such as curing diseases, or even change a person’s personality.
Despite the initial hullabaloo, the idea of finding an ideal blood substitute eventually faded into obscurity. It wasn’t until the 1980s, in the wake of the HIV crisis, that found renewed interest in finding an artificial replacement for blood.
While many manufacturers have blood replacement products in clinical trials today, there is currently still no truly safe and effective artificial blood product in the market.
How blood works
In the human body, blood is truly the river of life. It serves many important functions, including supplying the cells with oxygen, as well as carrying hormones, nutrients and waste to be used or excreted from different systems in the body.
This crimson delight sought after by both mosquitoes and vampires is composed of platelets and plasma, white cells, and the all-important red cells.
Plasma is extracellular material made up of water, salts and various proteins that along with platelets, encourages blood to clot. If you happen to scrape or cut yourself, proteins in the plasma react with air and harden to prevent further bleeding.
White blood cells are responsible for immune defence.
They seek out invading organisms or materials, and minimise their effects in the body.
Meanwhile, red blood cells are responsible for the transportation of oxygen and carbon dioxide throughout the body.
On the membranes of these red cells are proteins that the body recognises as its own. For this reason, a person can only use blood that is compatible with his type. This is why a doctor has to know the blood type of a patient in the event of a blood transfusion (using real blood), or there can be fatal consequences.
Also, real blood can be contaminated with viruses such as hepatitis or HIV, although this is quite unlikely to happen in most developed countries.
At present, the number of patients needing blood is outweighing supply. Perhaps the biggest challenge with real (human) blood is that it has a shelf life of only about 42 days and needs to be refrigerated, making it more difficult to keep in stock for emergencies and battlefield scenarios.
Many of us will have a hard time thinking about having our real blood replaced with the artificial version. Yet the technology for creating artificial blood is already in existense, and the idea of artificial blood for commercial use will likely become a reality over the next decade.
Currently, artificial blood products are designed only to replace the function of red blood cells. True blood serves various biological functions, but artificial blood operates on the sole purpose of transporting oxygen and carbon dioxide throughout the body, when it can no longer do so on its own.
For this reason, artificial blood is often referred to as an “oxygen therapeutic” and may be more appropriately named as “oxygen carriers”.
The ideal artificial blood product possesses the following characteristics. First, it must be safe to use and compatible within the human body. This means that anyone can be administered with artificial blood no matter what his or her blood type is.
It also means that artificial blood can be sterilised to kill bacteria and viruses, so the issue of transmitting diseases can be avoided.
Second, it must be able to transport oxygen throughout the body and release it where it is required.
Another aspect is that it must be shelf stable. Unlike donated blood, artificial blood can be stored for over a year or more, and does not need to be refrigerated.
This is beneficial for emergency situations and in battlefields. In addition, people who cannot accept transfusions of real blood due to religious reasons can accept transfusions of artificial blood.
There are currently two significantly different products that are being developed as blood substitutes. They differ primarily in the way that they carry oxygen. One is based on perfluorocarbons (PFC), while the other is a haemoglobin-based product.
PFC are biologically inert materials that can dissolve about 50 times more oxygen than blood plasma. Because they can be made without any biological materials, this eliminates the real possibility of spreading an infectious disease through blood transfusion. They are also relatively inexpensive to produce.
However, PFC-based blood products have two major setbacks. First, they are not soluble in water. To get them to work, they must be combined with emulsifiers – fatty compounds called lipids that are able to suspend tiny particles of PFC in the blood.
Second, they cannot carry as much oxygen as haemoglobin-based products, and this means that significantly more PFC must be used. One product of this type has been approved for use by the Federal Drug Administration (FDA), but has failed to gain commercial appeal because the amount required to provide a benefit is too high.
Improved PFC emulsions are being developed but have yet to reach the market.
Hemoglobin is a protein in red blood cells that carries oxygen from the lungs to the other tissues in the body. Artificial blood based on haemoglobin is premised on this natural function.
Unlike PFC products, where dissolving is the key mechanism, oxygen covalently bonds to haemoglobin. However, haemoglobin products are different from real blood in that they are not contained in a membrane so that the problem of blood typing does not exist.
However, raw haemoglobin cannot be used because it would break down into smaller, toxic compounds within the body. Another challenge is that most haemoglobin-based products last no more than 20-30 hours in the body. This compares to transfusions of whole blood that lasts 34 days.
There are also problems with the stability of haemoglobin in a solution. The challenge in creating a haemoglobin-based artificial blood is to modify the haemoglobin molecule so these problems are resolved. Strategies to stabilise haemoglobin have involved either chemically cross-linking molecules or using recombinant DNA technology to produce modified proteins.
Towards a bloody good future
Several companies are already working on the production of a safe and effective artificial blood substitute as we speak. However, these various blood substitutes in question all seem to suffer from certain limitations.
For instance, unlike true blood, they do not possess the ability to fight disease and clot. Current artificial blood technology are also limited to short-term blood replacement applications.
But while there are still controversies surrounding the use of artificial blood, it is reported that within the next decade, new materials to carry oxygen in the system will be found, generating an even more sophisticated and widespread artificial blood market.
Let’s just hope there won’t be another wave of sparkly vampires.