Influence of Molecular Structure on O2-Binding Properties and Blood Circulation of Hemoglobin‒Albumin Clusters

A hemoglobin wrapped covalently by three human serum albumins, a Hb-HSA 3 cluster, is an artificial O 2 -carrier with the potential to function as a red blood cell substitute. This paper describes the synthesis and O 2 -binding properties of new hemoglobin‒albumin clusters (i) bearing four HSA units at the periphery (Hb-HSA 4 , large-size variant) and (ii) containing an intramolecularly crosslinked Hb in the center (XLHb-HSA 3 , high O 2 -affinity variant). Dynamic light scattering measurements revealed that the Hb-HSA 4 diameter is greater than that of either Hb-HSA 3 or XLHb-HSA 3 . The XLHb-HSA 3 showed moderately high O 2 -affinity compared to the others because of the chemical linkage between the Cys-93(β) residues in Hb. Furthermore, the blood circulation behavior of 125 I-labeled clusters was investigated by assay of blood retention and tissue distribution after intravenous administration into anesthetized rats. The XLHb-HSA 3 was metabolized faster than Hb-HSA 3 and Hb-HSA 4 . Results suggest that the molecular structure of the protein cluster is a factor that can influence in vivo circulation behavior.