Acylation of human hemoglobin with polyoxyethylene derivatives

Hemoglobin Solutions Coupled with Polyethylene Glycol 1900: Preparation, Purification, Quality Control and Pharmacological Trials by Hemorrhagic Shock

The usefulness of hemoglobin solutions as oxygen transporters is limited by their high affinity for oxygen and rapid elimination from the circulation. Various chemical modifications of hemoglobin aimed at overcoming these two handicaps have been suggested. We have developed a conjugate of pyridoxylated human hemoglobin with monomethoxypolyoxyethylene 1900, whose preparation and properties are described. We present comparative results on short-term or definitive survival of Wistar rats which, during hemorrhagic shock due to the loss of 60 or 80% of their blood mass, were given a solution of native or modified hemoglobin, in some cases purified by ion-exchange chromatography to remove non-heme proteins, lipids, and some endotoxins. The more complex the treatment used to improve the properties and the purity of the hemoglobin solutions, the longer the animals survived. The loss of hemoglobin in the urine was greatly reduced after conjugation: after 20 h, less than 6% of the total infused.

Characterization, cell uptake, and subcellular distribution of DNA complexes with lipoglutamides having tetraethylene glycol tails

Lipoglutamides with tetraethylene glycol tails were synthesized. Physicochemical features of the DNA/lipoglutamide complexes were investigated by light scattering method, phase transition, and CD-spectrum. Aggregation of the DNA/lipoglutamide complex was significantly depressed compared with DNA complexes without ethylene glycol tails, and the solution showed no turbidity. The DNA/lipoglutamide complex showed a high resistance to nuclease, and an efficient internalization into tumor cells, compared with those of DNA alone. Furthermore, the DNA complex was found by confocal laser scanning fluorescence microscopy to distribute in the cytoplasmic region.

Immobilization of proteins on poly(methyl methacrylate) films

Polymethyl methacrylate (PMMA) films were treated by oxygen plasma discharge followed by acrylic acid (AA) grafting. The amount of carboxyl groups introduced by the grafting of AA on to the film surfaces was in the range 0.47-9.48 mumol/cm2, depending on the pressure of the plasma chamber during the discharge treatment. The carboxyl groups of the PMMA film surface previously activated with water soluble carbodiimide were coupled with bovine serum albumin, collagen and gelatin. The protein immobilization on the surface was confirmed by attenuated total reflection Fourier transform infra-red spectroscopy (ATR-FTIR) and electron spectroscopy for chemical analysis (ESCA). The amount of albumin, collagen and gelatin immobilized on the PMMA surface was 6.25, 7.25 and 13.75 micrograms/cm2, respectively, as determined by the coomassie brilliant blue-protein interaction. The water contact angle of the PMMA film was markedly decreased by oxygen plasma treatment, AA grafting or protein immobilization, indicating the increase of hydrophilicity of the surface-modified PMMA films. The protein-immobilized PMMA films may be widely used as a biocompatible material.

A potential blood substitute from carboxylic dextran and oxyhemoglobin. I. Preparation, purification and characterization

Human adult hemoglobin (Hb) from peripheral venous blood was covalently linked, under its oxygenated form, to a dextran polymeric effector to yield conjugates with low oxygen affinity. The polymeric effector was synthesized by directly coupling benzene tetracarboxylic anhydride to dextran (MW approximately 10,000) under mild conditions. The reaction parameters were chosen so that the resulting polymeric derivative was only very little cross-linked and possessed benzene tricarboxylate site concentrations lesser than 1 site for 10 glucose units, as it was found that for higher concentrations the polymer exhibited anticlotting properties. The reaction between oxyHb and the polymer (dex-BTC) was carried out in water in the presence of a water-soluble carbodiimide (EDCI). By optimization of the reaction conditions, a dextran-Hb conjugate with a P50 of 21 torr (37 degrees C, 50mM Bis-tris buffer pH 7.4, 0.14M NaCl, 40 mM glucose) and a potential O2 release of 0.30 ml/g Hb between oxygen partial pressures of 100 and 40 torr, was obtained. The viscosity and oncotic pressure of a solution containing about 6% of conjugated Hb were respectively 1.8 cSt (37 degrees C) and 28 torr (25 degrees C). This solution could be stored frozen at -20 degrees C for a long time, without modification of its properties.

Improvement of oxygen-carrying properties of human hemoglobin by chemical modification with a benzene hexacarboxylate-monosubstituted polyoxyethylene

Benzene hexacarboxylate-monosubstituted polyoxyethylene on contact with Hb decreases its oxygen affinity, probably because it specifically interacts with the amino groups of the phosphate-binding site. This site specificity was used to direct the covalent coupling of this polymeric reagent with hemoglobin, in the vicinity of this beta cleft in order to obtain conjugates with low oxygen affinity and well-defined molecular weight. Such conjugates could thus be regarded as potential candidates for blood substitutes. Covalent fixation of this polymeric site-labeling reagent onto hemoglobin was carried out with the oxy and the deoxy form in the presence of a water soluble carbodiimide. It turns out that the oxygen-binding properties of the resulting hemoglobin derivatives depend on the reaction conditions, yet in all cases the oxygen affinity of the modified protein was lower than that of native hemoglobin and was no longer affected by organic phosphates. These results indicate that phosphate-binding site amines are probably involved in the covalent coupling, although in some conjugates (especially those prepared with high ratios of reagents) other amino groups participate also in the linking to the polymer. Chromatographic analysis and tryptic peptide mapping of some conjugates evidenced that the beta-terminal valine residue was in fact the preferential binding site of hexacarboxylate-monosubstituted polyoxyethylene.

Magnetic urokinase: targeting of urokinase to fibrin clot

A plasminogen activator of human origin, urokinase, was endowed with magnetic property. The magnetic urokinase was composed of magnetite, polyethylene glycol derivative and urokinase, and dispersed in saline. Its particle size of magnetite was approximately 30-60 nm. It was selectively delivered to fibrin clot by magnetic force in continuously circulating plasma and exerted fibrinolytic activity without degrading fibrinogen.