Hemoglobin-albumin cluster: physiological responses after exchange transfusion into rats and blood circulation persistence in dogs.

A core-shell protein cluster comprising hemoglobin and human serum albumins, hemoglobin-albumin cluster (Hb-HSA3), was designed and synthesized for use as an artificial O2 carrier and red blood cell (RBC) substitute. For initial preclinical safety evaluation of the Hb-HSA3 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-HSA3 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-HSA3 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in a sham group (without infusion) and an HSA group (with HSA administration) for 6 h. Serum biochemical tests of the withdrawn blood indicated safety of the protein cluster.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-HSA3 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-HSA3 as an alternative material for use in RBC transfusion.

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-HSA3 cluster, is an artificial O2-carrier with the potential to function as a red blood cell substitute. This paper describes the synthesis and O2-binding properties of new hemoglobin‒albumin clusters (i) bearing four HSA units at the periphery (Hb-HSA4, large-size variant) and (ii) containing an intramolecularly crosslinked Hb in the center (XLHb-HSA3, high O2-affinity variant). Dynamic light scattering measurements revealed that the Hb-HSA4 diameter is greater than that of either Hb-HSA3 or XLHb-HSA3. The XLHb-HSA3 showed moderately high O2-affinity compared to the others because of the chemical linkage between the Cys-93(ß) residues in Hb. Furthermore, the blood circulation behavior of 125I-labeled clusters was investigated by assay of blood retention and tissue distribution after intravenous administration into anesthetized rats. The XLHb-HSA3 was metabolized faster than Hb-HSA3 and Hb-HSA4. Results suggest that the molecular structure of the protein cluster is a factor that can influence in vivo circulation behavior.

Safety Evaluation of Hemoglobin-Albumin Cluster "HemoAct" as a Red Blood Cell Substitute.

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 (125)I-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.

Hemoglobin-albumin cluster incorporating a Pt nanoparticle: artificial O2 carrier with antioxidant activities.

A covalent core-shell structured protein cluster composed of hemoglobin (Hb) at the center and human serum albumins (HSA) at the periphery, Hb-HSAm, is an artificial O2 carrier that can function as a red blood cell substitute. Here we described the preparation of a novel Hb-HSA3 cluster with antioxidant activities and its O2 complex stable in aqueous H2O2 solution. We used an approach of incorporating a Pt nanoparticle (PtNP) into the exterior HSA unit of the cluster. A citrate reduced PtNP (1.8 nm diameter) was bound tightly within the cleft of free HSA with a binding constant (K) of 1.1×10(7) M(-1), generating a stable HSA-PtNP complex. This platinated protein showed high catalytic activities for dismutations of superoxide radical anions (O2•-) and hydrogen peroxide (H2O2), i.e., superoxide dismutase and catalase activities. Also, Hb-HSA3 captured PtNP into the external albumin unit (K = 1.1×10(7) M(-1)), yielding an Hb-HSA3(PtNP) cluster. The association of PtNP caused no alteration of the protein surface net charge and O2 binding affinity. The peripheral HSA-PtNP shell prevents oxidation of the core Hb, which enables the formation of an extremely stable O2 complex, even in H2O2 solution.

Covalent core-shell architecture of hemoglobin and human serum albumin as an artificial O2 carrier.

Covalent core-shell structured protein clusters of hemoglobin (Hb) and human serum albumin (HSA) (HbX-HSAm) (m = 2, 3) with novel physiological properties were generated by linkage of Hb surface lysins to HSA cysteine-34 via an α-succinimidyl-ε-maleimide cross-linker (X: 1 or 2). The isoelectric points of HbX-HSAm (pI = 5.0-5.2) were markedly lower than that of Hb and almost identical to that of HSA. AFM and TEM measurements revealed a triangular Hb1-HSA3 cluster in aqueous medium. The complete 3D structure of Hb1-HSA3 based on TEM data was reconstructed, revealing two possible conformer variants. All HbX-HSAm clusters showed a moderately higher O2 affinity than the native Hb. Furthermore, the exterior HSA units possess a remarkable ability to bind lumiflavin (LF). The addition of NADH to an aqueous solution of the met-Hb2-(HSA-LF)3 cluster reduced the inactive ferric Hb center to the functional ferrous Hb. This O2-carrying hemoprotein cluster with strongly negative surface net charge, high O2 affinity, and NADH-dependent reductase unit can support a new generation of molecular architecture for red blood cell substitutes.