How to breathe underwater: the first synthetic red blood cells

Respirocytes are synthetic red blood cells, which may and will be able to replace the body's natural red blood cells in the circulation in the future. Inside the respiratory cells, the oxygen will be compressed at a particularly high density, and will be released slowly when there is a lack of oxygen in the blood, as happens in cases of drowning, heart attack and stroke

It happened at Ashdod beach, year 2020. One of the bathers at the men's beach was swept into the deep water and could not keep his head above water. Until the rescuer arrived, the victim spent half an hour under water and watched the fish with interest, as air bubbles came out of his mouth, indicating regular breathing. No oxygen balloon, no snorkel. He just needed the respirocytes in his body.

What are respirocytes? These are synthetic red blood cells, which may and will be able to replace the body's natural red blood cells in the bloodstream in the future. The respirocytes will be able to carry oxygen to the cells, just as normal red blood cells do, and that's why they got their name: respiro, ``breath'' and cytes, ``cells'' - ``breathing cells''. Inside the respiratory cells, the oxygen will be compressed at a particularly high density, and will be released slowly when there is a lack of oxygen in the blood, as happens in cases of drowning, heart attack and stroke. The victim of the accident or illness will be able to continue breathing for many minutes, until the rescue forces arrive.

If the respirocytes seem like a magic cure to you, you are right. This is a purely theoretical idea that was practiced by the theorist Robert Freitas Jr. ten years ago. Today, it is not possible to achieve such a level of compression of oxygen in such small and precise volumes, certainly not to create the slow and well-controlled release mechanism that would be required to prevent the compressed oxygen from exploding all at once out of the spirocytes and inflating the person like a balloon (an action that will certainly help improve his buoyancy, but will interfere with other basic biological operations, such as living). But despite the many problems, a new study was published less than two weeks ago, indicating that we are close to being able to produce artificial, man-made red blood cells.

The group of researchers, from Harvard Medical School, did not attempt to create respirocytes, nor did they pretend to. All they tried to do was create cell-like structures that could perform the role of red blood cells and transport oxygen in the bloodstream. This operation is more difficult than it sounds, because the blood corpuscles are real engineering marvels: they are strong and flexible, and have a discoid shape that allows them to squeeze through blood vessels that are smaller in diameter than the diameter of the blood corpuscle itself. They succeed where ordinary polymers, such as polystyrene, fail. The researchers realized that the existing materials and production methods were not suitable for the craft, so they came up with their own innovative way to create the synthetic red blood cells.

It is easy to understand the production process if you think of a balloon filled with air, coated with many layers of plasticine. If we poke the balloon with a pin through the soft sheath, it will explode into a thin strip of rubber - but the plasticine coating will retain its original shape. The remaining coating will also be soft and flexible enough to deform and change shape under pressure, thus allowing it to pass through pipes smaller than its maximum diameter.

Instead of a balloon, the researchers used synthetic spheres designed in a discoid shape and made of polymeric materials such as polystyrene and PLGA. The globules were coated with layer upon layer of hemoglobin and other proteins. Hemoglobin is the most important protein in the natural red blood cells, and it is the one that is able to bind the oxygen to it and release it near the hungry cells. Each globule was coated with several layers of proteins that created a flexible and thin sheath - which was also able to absorb oxygen from the environment. At the end of the coating process, the researchers melted the rigid polymeric base of the globule and thus only the protein layers that surrounded it remained, reflecting the globule's original shape and functioning in a similar way to a real red blood globule.

Tests conducted on the synthetic red blood cells proved that they can withstand mechanical forces similar to those of natural red blood cells, and can also pass through glass tubes thinner than their diameter, simulating extremely small blood vessels. These are still not respirocytes capable of storing compressed oxygen, but their ability to bind oxygen is impressive and identical to that of natural red blood cells that come from mouse blood, and they are able to maintain this ability even throughout an entire week of experiment.

This is already an impressive progress towards creating a synthetic blood substitute that can deliver oxygen to all the hidden corners of the body and can reduce the need for blood donations. The researchers note that the globules can also be coated with layers of other substances besides hemoglobin, such as drugs that will be slowly released into the blood. But will the dream of the respirocytes come true from here? It must be admitted that these are still many years away from us, and we will have to go through many more hurdles until we reach a technology sophisticated enough to produce them. The optimists will say that we have crossed one more hurdle. The pessimists will stop reading at this point.

The article in the blog ofRoey Tsezana - a different science