Oxygen transporting ability of lipidheme microspheres as a totally synthetic red cell substitute

O₂ Binding parameters, O₂ solubility and in vivo O₂ transporting ability of a lipidheme microsphere as a totally synthetic red cell substitute are described. The O₂-binding affinity of the lipidheme microsphere (P_1/2(O₂): about 40 torr at 37°C) was slightly lower than that of human blood, and its O₂ association and dissociation rate constants were larger than those of hemoglobin. The O₂ solubility of this solution was estimated; an aqueous solution containing a high amount of dissolved oxygen can be prepared by prescription. The lipidheme microsphere suspension was intravenously injected into hemorrhagic beagles and the circulation lifetime of each constituent of the artificial red cell was determined. The O₂ consumption by the lipid-heme was estimated to be about 15% of the total O₂ consumption. These results suggest that the lipidheme microsphere has the ability to act as an oxygen carrier in the blood stream.