A New Blood Substitute

Since blood donors are in short supply and donated blood only lasts 40 days, scientists have for a century tried to find a human blood alternative.  

In the 1870s, milk was explored as a substitute. Much later, perfluorocarbon was tried for its stability and ability to absorb oxygen in the lungs, but it had too many side effects.  

Today, some researchers are focused on hemoglobin, an ingredient in the blood that gives blood cells their color. The red molecule binds oxygen and distributes it throughout the body.   

So far, the most promising study uses recycled hemoglobin from a blood bank’s expired blood, and here’s how it works. Around ten thousand copies of hemoglobin protein are placed inside a lipid sac, resembling a mini-red blood cell. Inside are also molecules called 2,3-DPG that make the cell-like capsules responsive to changes in pH.  This means they respond differently to acidity or alkalinity. At the high pH inside the lung, 2,3-DPG interacts with hemoglobin increasing its ability to bind oxygen.    

In other tissues and organs, where the pH is low, the 2,3-DPG is released which causes the hemoglobin to release oxygen into those tissues. This mimics how our red blood cells work naturally.   

 These engineered hemoglobin sacs are compatible with all blood types, don’t need refrigeration, and have a shelf life of 2 years. So far, animal testing is going well and the next step is human clinical trials.