[Artificial blood]

To prepare for shortage of blood components and to avoid side effects such as blood borne infectious disease, blood substitutes such as artificial red cell (artificial oxygen carrier) and artificial platelet are being developed. As for oxygen carriers, there are several candidates such as perfluorochemicals, modified hemoglobins and liposome encapsulated hemoglobins and albuimin heme. Perfluorochemicals have limited oxygen carrying capacity and oxygen inhalation is mandatory when they are used. Modified hemoglobins such as intermolecular or intramolecular cross linked hemoglobins have side effect to cause hypertension by scavenging nitro oxide (NO) which is produced by endothelial cells, because the size of these hemoglobins are small enough to go to the adjacent place near endothelial surface. Hemoglobin vesicles (HbV) in which hemoglobins are encapsulated in liposome is most possible candidate for oxygen carrier. Usefulness and safety of the HbV is evidenced by animal shock model or exchange transfusion model and they are now being prepared for clinical trials as red blood substitutes or oxygen therapeutics. Albumin heme in which recombinant human serum albumin incorporating synthetic heme is thought an ideal resuscitation fluid as this material has colloid oncotic pressure. Short time storage and viral infection are serious concern in platelet transfusion therapy for bleeding thrombocytopenic patients. Adhesion of the platelet to the collagen surface and aggregation at the bleeding sites to plug holes in blood vessels, and to facilitate the function of the remaining platelets is a starting point in developing platelet substitutes and several platelet substitutes have been proposed on this theory.