Differences in Particle Size and Oxygen-Binding Affinity Between Cross-Linked Hemoglobin and Hemoglobin Vesicle

Summary

Modified hemoglobins (Hb) such as intramolecular cross-linked Hb are currently undergoing clinical tests. On the other hand, a Hb vesicle that encapsulates a purified and concentrated Hb solution with the bilayer membrane of phospholipids is expected to overcome the problems of the modified Hb. The differences in size and oxygen-binding affinity of the Hb vesicles and intramolecular cross-linked Hb were compared to discuss the difference in the cellular and acellular types of Hb-based oxygen carriers, which have oxygen-binding and dissociation equilibrium curves similar to those of red blood cells (RBCs). The particle sizes of the cross-linked Hb, the Hb vesicle, and RBC are 5, 250, and 8000nm, respectively. The Hb solution shows the lowest viscosity, whereas the viscosity of the Hb vesicle is relatively high and similar to the RBC. The permeability of the membrane filters depends on the particle size: cross-linked Hb > Hb vesicles > RBC. The oxygen-binding and -releasing rates of the Hb vesicles are between those of the acellular Hb and RBC, which could be explained in terms of the total surface area of Hb and the oxygen diffusion in the concentrated Hb solution (36g/dl) inside the Hb vesicle.