Physical Properties of Hemoglobin Vesicles as Red Cell Substitutes

Abstract

Hemoglobin vesicles (HbV) as red cell substitutes were prepared from a purified carbonylhemoglobin (HbCO) solution and a lipid mixture composed of phospholipids, cholesterol, and alpha-tocopherol. The diameter was controlled to 251 +/- 87 nm using an extrusion method; the vesicles penetrated through the membrane filters with regulated pore sizes. After the ligand exchanging reaction (HbCO-->HbO2), the oxygen affinity (P50) of HbV was 32 Torr, which was controlled with the coencapsulation of pyridoxal 5'-phosphate. The rate of metHb formation in HbV was nonenzymatically reduced with the coencapsulation of DL-homocysteine. The Hb concentration of the HbV suspension, which was dispersed in a phosphate buffered saline solution (pH 7.4), was controlled at 10 g/dL. At this concentration, the total lipid concentration was 6.2 g/dL and the viscosity, 2.6 cP (230 s-1), was lower than that of the blood (4.4 cP). The HbV suspension showed a typical non-Newtonian flow for a particle dispersion and agreed well with the Casson model. The viscosity at shear rates lower than 23 s-1 showed a maximum with increasing the mixing ratio of human blood, plasma, or albumin, while no maximum was observed for the mixture with washed red blood cells. The aggregates of HbV are formed by interaction with plasma proteins, including albumin, while the aggregates reversibly dissociate at higher shear rate.

Polymersome Encapsulated Hemoglobin: A Novel Type of Oxygen Carrier

“…This was true even for L1 PEH dispersions, which were expected to have ∼35 nm hydrophobic membrane thickness. The P 50 and n of PEH dispersions were also comparable to values measured for PEGLEHs, 14,15,40,60,63 LEAcHbs, 41 and nonmodified LEHs. 29 However, the P 50 s of lipogel particles and NHPs encapsulating Hb were reported to be lower than that of human RBCs, which indicated an increase in Hb oxygen affinity caused by cross-linking the encapsulated Hb into the hydrogel polymer matrix.…”

PEGylated liposomes encapsulating human hemoglobin enhance oxygen transfer and cell proliferation while decreasing cell hypoxia in fibrin

“…[metHb] ≤ 2%; pH at 37 • C = 7.4) [37,44,45]. Pyridoxal 5 -phosphate (PLP) (18 mM) was also encapsulated with hemoglobin to yield an estimated P 50 of 30 Torr [44,46,47].…”

“…Pyridoxal 5 -phosphate (PLP) (18 mM) was also encapsulated with hemoglobin to yield an estimated P 50 of 30 Torr [44,46,47]. Hemoglobin function to load and unload oxygen was assessed using visible-light spectroscopy, as previously described [37].…”

Haemoglobin, oxygen carriers and perioperative organ perfusion

“…Theoretical advantages of this product include longer intravascular half-time (in the order of days), less vasoconstriction and the possibility to include other useful substances such as 2,3-DPG or methaemoglobin-reductase to regulate O 2 affinity and decrease methaemoglobine formation [54,138,139], other enzymes such as catalase or superoxid-dismutase can be co-encapsulated as well which may prove beneficial during reperfusion of hypoxic areas for reducing the reperfusion injury [140]. Although the neo red cell technology may enable fascinating combinations of heamoglobins and diverse enzymes, a clinical application appears unlikely in the near future.…”