“Artificial Blood” : Part I

June 10, 2013 by tildabarliya

“Artificial blood” has been the main focus of research in the past few years (1) and refers to a substance used to mimic and fulfill some functions of biological function.  Author: Tilda Barliya PhD

A number of driving forces have led to the development of artificial blood substitutes (1):

1.  The military, which requires a large volume of blood products that can be easily stored and readily shipped to the site of casualties.
2.  HIV; with the advent of this virus, the medical community and the public suddenly became aware of the significance of transfusion-transmitted diseases and became concerned about the safety of the national blood supply.
3. The growing shortage of blood donors. Approximately 60% of the population is eligible to donate blood, but fewer than 5% are regular blood donors.
4. Short shelf-life of the blood products.
5. High hospital needs: cancer patients, transplantation etc

Artificial blood products offer many important benefits:

• Readily available
• Have a long shelf life
• Can undergo filtration and pasteurization processes
• Do not require blood typing (i.e A,B AB, O)
• Do not appear to cause immunosuppression in the recipient.

Researchers have focused their efforts on creating artificial substitutes for 2 important functions of blood: A) oxygen transport by red blood cells and B) hemostasis by platelets (1).

A) Red Cell Substitutes:

• Hemoglobin based
• Perfluorocarbon (PFC) based

A1) Hemoglobin-based

The hemoglobin-based substitutes use hemoglobin from several different sources (1):

• Human – Human hemoglobin is obtained from donated blood that has reached its expiration date and from the small amount of red cells collected as a by-product during plasma donation.
• Animal – Animal hemoglobin is obtained from cows. This source creates some apprehension regarding the possible transmission of animal pathogens, specifically bovine spongiform encephalopathy.
• Recombinant – Recombinant hemoglobin is obtained by inserting the gene for human hemoglobin into bacteria and then isolating the hemoglobin from the culture.

Understanding hemoglobin, its transition from a monomer to a tetramer and the way it needs to be linked to the surface of the artificial blood cells is of major issue and will be discussed in more depth in part II.

A2) Perfluorocarbon (PFC) based

PFCs are synthetic hydrocarbons with halide substitutions and are about 1/100th the size of a red blood cell. These solutions have the capacity to dissolve up to 50 times more oxygen than plasma. Because PFC solutions are modified hydrocarbons, however, they do not mix well with blood and must be emulsified with lipids or oils. The PFCs are inert products. After infusion, the molecules vaporize and are then exhaled over several days (1).

B) Platelet Substitutes:

Platelets are also at very high need due to their extremely short shelf-life (5 days) and very limited supply. Several methods have been utilized to create platelet substitutes including:

• Infusible platelet membranes
• Thrombospheres
• Lyophilized human platelet product

Use and need for HLA antigen or platelet antigens, fibrinogen proteins and aggregation factors will be further discussed in part II.

In Summary:

The growing need for blood supply due to short shelf-life, limited supply and increase in disease/injured population have urged researchers to look for blood substitutes.   Although the many years of research and profound progress that have been made, there’s plenty of disadvantages having complications and  limited clinical benefits. The topic of blood substitutes will be further discussed in part II, highlighting the different substitutes that were developed, those which entered clinical trails, and the potential use of nanotechnology in this field of research.

Reference:

1. Lesley Kresie. Artificial blood: an update on current red cell and platelet substitutes. Proc (Bayl Univ Med Cent). 2001 April; 14(2): 158–161 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1291332/

2. By: Tony Rairden. Synthetic Red Blood Cells Developed. http://www.nanotech-now.com/news.cgi?story_id=35993

3. By: Abdu I. Alayash. BLOOD SUBSTITUTES: Working to Fulfill a Dream. FDA voice. http://blogs.fda.gov/fdavoice/index.php/2012/06/blood-substitutes-working-to-fulfill-a-dream/

4. Jiin-Yu Chen, Michelle Scerbo, and George Kramer. A Review of Blood Substitutes: Examining The History, Clinical Trial Results, and Ethics of Hemoglobin-Based Oxygen Carriers. Clinics (San Paulo) 2009 August; 64(8): 803-813. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2728196/