A hemoglobin (Hb) wrapped covalently by human serum albumins (HSAs), a core–shell structured hemoglobin-albumin cluster designated as “HemoAct”, is an O2-carrier designed for use as a red blood cell (RBC) substitute. This report describes the blood compatibility, hemodynamic response, and pharmacokinetic properties of HemoAct, and then explains its preclinical safety. Viscosity and blood cell counting measurements revealed that HemoAct has good compatibility with whole blood. Intravenous administration of HemoAct into anesthetized rats elicited no unfavorable increase in systemic blood pressure by vasoconstriction. The half-life of 125I-labeled HemoAct in circulating blood is markedly longer than that of HSA. Serum biochemical tests conducted 7 days after HemoAct infusion yielded equivalent values to those observed in the control group with HSA. Histopathologic inspections of the vital organs revealed no marked abnormality in their tissues. All results indicate that HemoAct has sufficient preclinical safety as an alternative material for RBC transfusion.

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A core-shell protein cluster comprising hemoglobin and human serum albumins, hemoglobin-albumin cluster (Hb-HSA 3), was designed and synthesized for use as an artificial O 2 carrier and red blood cell (RBC) substitute. For initial preclinical safety evaluation of the Hb-HSA 3 solution, we observed blood compatibility in vitro, physiological responses after exchange transfusion into rats and blood circulation lifetime in dogs. Dilution of human whole blood with Hb-HSA 3 showed an appropriate decrease in blood cell number, proportional to the mixing volume ratio. Time courses in the circulation parameters and blood gas parameters after 20% exchange transfusion with Hb-HSA 3 in anesthetized rats were almost identical to those observed in a sham group (without infusion) and an HSA group (with HSA administration) for 6 h. Serum biochemical tests of the withdrawn blood indicated safety of the protein cluster. Furthermore, fluorescent Hb-HSA 3 was infused into beagle dogs to assess blood retention. Fluorescence measurements of the blood samples enabled us to ascertain the cluster half-life within the intravascular space. Histopathologic inspections of the vital organs imply no abnormality in tissues. All these results indicate sufficient initial preclinical safety of Hb-HSA 3 as an alternative material for use in RBC transfusion.

Core-shell protein cluster comprising a hemoglobin (Hb) in the center and human serum albumins (HSA) at the exterior, Hb-HSA 3 cluster, is an artificial O 2 -carrier designed for use as a red blood cell (RBC) substitute. Lyophilization of the Hb-HSA 3 cluster solution ([Hb unit] = 5 g/dL) with sucrose and trehalose yielded stable pink powder, which can be stored for 2 years at 4 C. Addition of pure water to the powder regenerated the homogeneous solution. The O 2 -binding properties and oxyHb rate have been unaltered during the storage period. Infrared spectroscopic studies revealed that the hydrogen bond between protein and sugar stabilizes threedimensional structure of the cluster.