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.