Artificial Blood: Searching in Vein

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Blood is the elixir of life. The essence of human functioning. A life-giving river flowing with the elements that humans depend on for every breath, every movement, every second of consciousness. It is this very fluid that pulses through the body to transport oxygen to thirsty cells. It trucks waste to the kidneys and mitigates blood loss through clotting. It delivers chemical messages through hormones and contains the soldiers that are white blood cells to defend against pathogens. It is not surprising therefore that its many functions make it necessary for survival.

But blood is a rare commodity. It is of high demand and comparatively low supply, and even lower in lower-income countries. It is estimated for example, that 25 donations per 1000 should suffice in a country, but the blood donation rate is just 6.8 donations in lower-middle-income countries and 5.0 in low-income countries. This supply is expected to meet a need for blood every 3 seconds. A drastic difference in demand and supply has created a worldwide shortage that must be filled. Thus the quest for artificial blood has thrived in recent years. The huge demand also makes the endeavour to copy blood a lucrative one. Though most progress has been made in the last few decades, this imitation game began in the 1600s.

It was then when various, strange liquids were used to replace blood. Such liquids included milk, urine, beer, sheep’s blood and saline solutions. All of these resulted in subsequent threat to the patient’s life or were forgotten for their unorthodox results. Milk for example, was first thought to be a success but then, many practitioners remained sceptical as to its true effect on the body; it never found widespread appeal. Beer was another interesting one- it’s weird to think how yeast was once used to copy a collection of living cells as complex as they come, but it too was a contender in the race. Since these ill-fated attempts, technology has given scientists a better chance to crack this puzzle.

Until very recently, scientists adopted two main strategies: haemoglobin-based oxygen-carriers (HBOCs) or per-fluorocarbons (PFCs). These strategies mimicked the main function of blood: to transport oxygen, while also performing other minor functions (usually ineffectively).

Let’s consider the former: haemoglobin-based oxygen-carriers (HBOCs). These are synthetic made haemoglobin molecules that act just like Hb molecules in our blood. Though this is simple enough to understand, the problems are extensive and hard-to-tackle. For starters, it tends to accumulate to toxic levels in the blood since the molecule is not inside a red blood cell but instead isolated. One study analysed HBOC clinical trials and concluded a three-fold increase in the risk of heart attacks in people who received the substitutes vs donor blood. As well as this lies the problem of renal failure. Administration of HBOCs has led to kidney dysfunction in many instances in trials.

Now let’s explore the latter of the two: per-fluorocarbons (PFCs). These liquid compounds are often used for coatings in products like furniture, food packaging and electrical wire insulation. Scientists (led by biochemist Leland Clark) found droplets of the chemicals could dissolve and transport oxygen in its liquid core, though slower than haemoglobin. It was a major breakthrough, until subsequent trials revealed that these too were a danger to cardiac and renal function.

The field went dark until recently, now, there’s a thaw in the field.”

Dr. Dipanjan Pan, a bioengineering professor

Scientists have realised that mimicking nature is an endless endeavour with unlikely fruition. So why not copy just one function of blood- to be used when that role of blood is compromised; like clotting. This would be a crucial invention to prevent bleeding out. Some labs are developing nano-structures that promote accumulation of platelets, others are focusing on developing synthetic nanotechnology coated with specific proteins to quicken the clotting process. If not clotting, then perhaps oxygen-delivery. ErythroMer is an artificial red blood cell to be injected during severe blood loss. It ensures that organs don’t fail after blood loss cannot provide them with oxygen. These inventions essentially act as a bridge between the accident and the operation theatre; they ‘keep the patient alive’. Labs are no longer looking at blood substitution as a holy grail of medicine; they have dissected it into a much simpler problem.

So, can we expect to see a man-made recreation of one of nature’s phenomena. Probably not… But the future is not at all bleak. Various recent developments mean the next decade will be an innovative and life-saving one. One where there will be oxygen-delivery alternatives readily available in the ambulance in the case of a trauma injury. One where there will be clotting-substitutes to save blood after a haemorrhage. The coming decade will likely redefine the field of medicine itself while saving many lives and closing the chapter of a centuries-old pursuit.


References

  1. World Health Organisation “Blood safety and availability” (2008) https://www.who.int/news-room/fact-sheets/detail/blood-safety-and-availability
  2. NCBI “The history of artificial blood” (2008) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2738310/
  3. Food and Drug Administration “Evaluating the Safety and Efficacy of Haemoglobin Blood Substitutes” (2018) https://www.fda.gov/vaccines-blood-biologics/biologics-research-projects/evaluating-safety-and-efficacy-hemoglobin-based-blood-substitutes
  4. UBC “Cell-Free Haemoglobin Blood Substitutes and Risk of Myocardial Infarction and Death” (2008) http://www.ubccriticalcaremedicine.ca/academic/jc_article/JAMA%20hb%20substitutes%20safety%202008%20(Sep-11-08).pdf
  5. Popsci “Searching in vein: a history of artificial blood” (2019) https://www.popsci.com/artificial-blood-history-science/
  6. Company About Page “Discover ErythroMer” (2020) http://www.kalocyte.com

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