title: Synthesis and physicochemical characterization of a series of hemoglobin-based oxygen carriers: objective comparison between cellular and acellular types.
abstract: A series of hemoglobin (Hb)-based O(2) carriers, acellular and cellular types, were synthesized and their physicochemical characteristics were compared. The acellular type includes intramolecularly cross-linked Hb (XLHb), polyoxyethylene (POE)-conjugated pyridoxalated Hb (POE-PLP-Hb), hydroxyethylstarch-conjugated Hb (HES-XLHb), and glutaraldehyde-polymerized XLHb (Poly-XLHb). The cellular type is Hb-vesicles (HbV) of which the surface is modified with POE (POE-HbV). Their particle diameters are 7 +/- 2, 22 +/- 2, 47 +/- 17, 68 +/- 24, and 224 +/- 76 nm, respectively, thus all the materials penetrate across membrane filters with 0.4 microm pore size, though only the POE-HbV cannot penetrate across the filter with 0.2 microm pore size. These characteristics of permeability are important to consider an optimal particle size in microcirculation in vivo. POE-PLP-Hb ([Hb] = 5 g/dL) showed viscosity of 6.1 cP at 332 s(-1) and colloid osmotic pressure (COP) of 70.2 Torr, which are beyond the physiological conditions (human blood, viscosity = 3-4 cP, COP = ca. 25 Torr). XLHb and Poly-XLHb showed viscosities of 1.0 and 1.5 cp, respectively, which are significantly lower than that of blood. COP of POE-HbV is regulated to 20 Torr in 5% human serum albumin (HSA). HES-XLHb and POE-HbV/HSA showed comparable viscosity with human blood. Microscopic observation of human red blood cells (RBC) after mixing blood with POE-PLP-Hb or HES-XLHb disclosed aggregates of RBC, a kind of sludge, indicating a strong interaction with RBC, which is anticipated to modify peripheral blood flow in vivo. On the other hand, XLHb and POE-HbV showed no rouleaux or aggregates of RBC. The acellular Hbs (P(50) = 14-32 Torr) have their specific O(2) affinities determined by their structures, while that of the cellular POE-HbV is regulated by coencapsulating an appropriate amount of an allosteric effector (e.g., P(50) = 18, 32 Torr). These differences in physicochemical characteristics between the acellular and cellular types indicate the advantages of the cellular type from the physiological points of view.
authors.affiliation: Department of Polymer Chemistry, Advanced Research Institute for Science and Engineering, Waseda University, Tokyo 169-8555, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Sakai
authors.forename: M
authors.initials: M
authors.lastname: Yuasa
authors.forename: H
authors.initials: H
authors.lastname: Onuma
authors.forename: S
authors.initials: S
authors.lastname: Takeoka
authors.forename: E
authors.initials: E
authors.lastname: Tsuchida
mesh_terms: D001802:Blood Substitutes / Q000138:chemical synthesis* / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology; D003102:Colloids / Q000737:chemistry; D004903:Erythrocyte Aggregation / Q000187:drug effects; D004912:Erythrocytes / Q000187:drug effects; D005976:Glutaral / Q000097:blood / Q000737:chemistry; D006454:Hemoglobins / Q000138:chemical synthesis* / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology; D006801:Humans; D006895:Hydroxyethyl Starch Derivatives / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism; D008970:Molecular Weight; D009997:Osmotic Pressure; D010100:Oxygen / Q000008:administration & dosage / Q000097:blood / Q000737:chemistry*; D010316:Particle Size; D011092:Polyethylene Glycols / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism; D014783:Viscosity
chemical_list: D001802:Blood Substitutes; D003102:Colloids; D006454:Hemoglobins; D006895:Hydroxyethyl Starch Derivatives; D011092:Polyethylene Glycols; D010100:Oxygen; D005976:Glutaral