Donated blood is screened, tested, and stored for up to 6 weeks. If it is kept longer that 6 weeks it is considered outdated and can't be used for transfusions. Hemosol Inc. of Etobicoke, Ontario uses this outdated blood to make a product called Hemolink which is a red blood cell substitute that can be used for transfusions.
Blood consists of red and white blood cells, plasma, and platelets.
The red blood cells contain hemoglobin which can bind and subsequently release oxygen. Hemoglobin, a protein, is a tetramer consisting of four parts each of which binds an xygen molecule. In order to produce the Hemolink the red blood cells are first separated from the other components in the blood. Secondly, the hemoglobin is extracted from the red blood cells and heated. The heat treatment ensures that no viruses remain that may have been overlooked in the screening process.