Another advantage of the substitute is that it is compatible with all blood types due to its surface structure, and it is therefore expected to be especially useful in times of disasters such as earthquakes. The group said the artificial cells each have a diameter of 250 nanometers, or one-fortieth the diameter of a regular red blood cell. One nanometer is equal to one-billionth of a meter. The diameter of the thinnest capillary is about half that of red blood cells. One of the difficulties in manufacturing an effective substitute for red blood cells was simulating their pliability.
Regular cells can change their shape to pass through the thinnest of vessels.
Due to their size, however, hemoglobin vesicles can travel freely through such vessels without escaping. In the United States, scientists have been working on the development of a substitute for red blood cells since the 1980s by directly processing hemoglobin molecules. However, they found that the substitutes were so small that they would escape from crevices in cells. As a result, blood vessels would contract, causing side effects such as increased blood pressure. Research into developing artificial red blood cells by processing hemoglobin molecules continues, but scientists have yet to eliminate these side effects.