Biocompatibility of Hemoglobin Vesicles, a Cellular-Type Artificial Oxygen Carrier, on Blood Cells and Plasma Proteins In Vitro and In Vivo

Abstract

Hemoglobin vesicles (HbV), cellular-type artificial oxygen carriers, are human hemoglobin encapsulated within a phospholipid bilayer membrane. Because HbV are injected intravenously, the biocompatibility of the HbV with blood components is extremely important to ensure their safety for clinical use. We evaluated this biocompatibility by particularly examining the influence of HbV on human blood cells and on plasma proteins in vitro. (1) Regarding influences to platelets that are involved not only in hemostasis but also in inflammation, HbV themselves neither activate platelets nor show aberrant effect on agonist-induced platelet activation. (2) HbV do not affect the agonist-induced activation of neutrophil functions that play important roles in innate immunity. (3) HbV do not affect hematopoietic progenitor activity. (4) The HbV examined herein (containing DHSG) do not activate the complement system, but old-type HbV (containing DPPG, no PEG modification) do so to a marked degree. (5) Neither coagulation nor the kallikrein–kinin cascade was affected by the current type of HbV. (6) Multiple HbV infusions in rats cause a transiently slight decrease in the complement titer only after first infusion, with no allergic reaction. No anaphylactic shock was observed in rats administered multiple empty vesicles without hemoglobin. (7) Infusion of HbV can “transiently” render HbV phagocytized-splenic cells immunosuppressive in ex vivo culture condition. Results of our in vitro and in vivo investigations show that HbV are highly biocompatible with human blood cells, human plasma proteins and rat immune systems.