In vitro andin vivo stability of polymerized mixed liposomes composed of 2,4-octadecadienoyl groups of phospholipids

The American Journal of Pathology

Horinouchi

Tomiyama

et al. 2001

100

Hemoglobin-vesicles (HbV) have been developed for use as artificial oxygen carriers (particle diameter, 250 nm) in which a purified Hb solution is encapsulated with a phospholipid bilayer membrane. The influence of HbV on the reticuloendothelial system was studied by carbon clearance measurements and histopathological examination. The HbV suspension ([Hb] = 10 g/dl) was intravenously infused in male Wistar rats at dose rates of 10 and 20 ml/kg, and the phagocytic activity was measured by monitoring the rate of carbon clearance at 8 hours and at 1, 3, 7, and 14 days after infusion. The phagocytic activity transiently decreased one day after infusion by about 40%, but it recovered and was enhanced at 3 days, showing a maximum of about twice the quiescent level at 7 days, and then returned to the normal value at 14 days. The initial transient decreased activity indicates a partly, but not completely, suppressed defensive function of the body. The succeeding increased phagocytic activity corresponds to the increased metabolism of HbV. The histopathological examination with anti-human Hb antibody, hematoxylin/eosin, and oil red O stainings showed that HbV was metabolized within 7 days. Hemosiderin was very slightly confirmed with Berlin blue staining at 3 and 7 days in liver and spleen, though they completely disappeared at 14 days, indicating that the heme metabolism, excretion or recycling of iron proceeded smoothly and iron deposition was minimal. Electron microscopic examination of the spleen and liver tissues clearly demonstrated the particles of HbV with a diameter of about 1/40 of red blood cells in capillaries, and in phagosomes as entrapped in the spleen macrophages and Kupffer cells one day after infusion. The vesicular structure could not be observed at 7 days. Even though the infusion of HbV modified the phagocytic activity for 2 weeks, it does not seem to cause any irreversible damage to the phagocytic organs. These results offer important information for evaluating the safety issues of HbV for clinical use.

Section: Discussionmentioning

confidence: 99%

Hemoglobin-Vesicles as Oxygen Carriers

The American Journal of Pathology

Horinouchi

Tomiyama

et al. 2001

100

“…This method produces enormously stable liposomes, like rubber balls, which are resistant to freeze‐thawing, freeze‐drying and rehydration [37–39]. However, the polymerized liposomes were so stable that they were not degraded easily in the macrophages, even 30 days after injection [40]. It was concluded that polymerized lipids would not be appropriate for intravenous injection.…”

Section: Stabilized Hbv For a Long‐term Storagementioning

confidence: 99%

Haemoglobin‐vesicles as artificial oxygen carriers: present situation and future visions

Journal of Internal Medicine

Sou

Horinouchi

et al. 2007

During the long history of development of haemoglobin (Hb)-based O2 carriers (HBOCs), many side effects of Hb molecules have become apparent. They imply the physiological importance of the cellular structure of red blood cells. Hb-vesicles (HbV) are artificial O2 carriers that encapsulate concentrated Hb solution with a thin lipid membrane. We have overcome the intrinsic issues of the suspension of HbV as a molecular assembly, such as stability for storage and in blood circulation, blood compatibility and prompt degradation in the reticuloendothelial system. Animal tests clarified the efficacy of HbV as a transfusion alternative and the possibility for other clinical applications. The results of ongoing HbV research make us confident in advancing further development of HbV, with the expectation of its eventual realization.

“…This method produces enormously stable liposomes, resembling rubber balls, which are resistant to freeze‐thawing, freeze‐drying and rehydration 55,56 . However, the polymerized liposomes were so stable that they were not degraded easily in the macrophages, even 30 days after injection 57 . It became widely believed that polymerized lipids are inappropriate for intravenous injection.…”

Section: Structural Stabilization Of Encapsulated Hemoglobin For Stocmentioning

confidence: 99%

Solution to the problems of acellular hemoglobins by encapsulation and the intrinsic issues of hemoglobin vesicles as a molecular assembly

Transfus Alt Transfus Med

Sou

Tsuchida

2007

SUMMARY Hemoglobin vesicles (HbV), or liposome‐encapsulated hemoglobins, are developed as artificial oxygen carriers for the use as a transfusion alternative. The safety and efficacy of HbV have been clarified in detail: HbV can overcome the side effects of hemoglobin (Hb) molecules (stroma‐free, and intra‐ or intermolecularly crosslinked) such as vasoconstriction, hypertension and possible vascular damage induced by direct contact of the vascular surface with Hb. On the other hand, intrinsic issues related to the suspension of HbV as a molecular assembly have to be considered: blood compatibility, structural and dispersion stabilities of the vesicles, and the requirement of prompt degradation in the reticuloendothelial system. Having overcome these issues, the results make us confident in advancing further development of HbV. Easy manipulation of physicochemical parameters of HbV provides possibilities for various clinical applications in addition to their use as a transfusion alternative.