Synthesis and properties of polymerized, diaspirin cross-linked hemoglobins

During the course of our studies it became clear that there were therapeutic applications for which a polymeric hemoglobin having an extended half-life in circulation would be appropriate. Therefore, a process for the glutaraldehyde-polymerization of diaspirin cross-linked hemoglobin (DCLHb) was developed and used to prepare glutaraldehyde-polymerized DCLHb (GP-DCLHb) in lactated Ringer's solution in sufficient quantities for biological testing. Both isovolemic exchange-transfusion and "top-load" studies (rats; primates and swine, respectively) were completed in which a broad spectrum of physiologic, histopathologic and analytical parameters were monitored and assessed. In general, GP-DCLHb in lactated Ringer's solution was well-tolerated physiologically. When compared to DCLHb, GP-DCLHb offers the advantages of reduced renal clearance of hemoglobin and an extended half-life in circulation. GP-DCLHb has the disadvantages that (1) glutaraldehyde is an ineffective virucidal agent under the conditions of the polymerization reaction and a separate virus inactivation step is required; (2) low-endotoxin (LAL-negative) GP-DCLHb solutions are pyrogenic (rabbits); and (3) unusual deposition of hemoglobin-containing material in the small arterioles of the liver and kidney (rats) was sometimes seen even after a period of time (2 weeks) during which treatment-related organ pathologies are usually resolved, a finding peculiar to GP-DCLHb among the various hemoglobin derivatives we have tested.