Design of nonhypertensive conjugated hemoglobins as novel resuscitation fluids

Enhancing the molecular size/volume Hb was introduced, as a simple molecular approach to overcome or attenuate the extravasation mediated NO scavenging activity of Hb in vivo. Conjugation of Hb, as a chemical tool to achieve this objective, has now advanced beyond this initial concept. It requires us now to recognize that engineering of resuscitation fluids like properties to Hb is a novel concept and simple approach to neutralize/attenuate the in vivo hypertensive activity of acellular Hb. Development of conjugated hemoglobins is reviewed here as it lead to the development of this concept along with future perspectives. Extension Arm chemistry, that integrates the concepts of click chemistry into the various conjugation approaches of relevance to this aspect of blood substitute research is discussed. Bridging these approaches to increase the efficacy of engineering resuscitation fluid like properties to Hb is suggested as the future direction of designing conjugated Hbs as oxygen therapeutics. The integration of site directed mutagenesis to tame the molecular properties of Hb with the extension arm facilitated PEGylation to attenuate the impact of conjugation chemistry and/or conjugated polymer on the tertiary/quaternary structure of the Hb molecule is discussed in detail as applied to PEGylation of Hb as the conjugation approach of choice to generate nonhypertensive Hb as oxygen therapeutics. We conclude that such a synergistic approach will result in the attenuation of heme degradation product dependent and oxidative stress mediated in vivo toxicity as well as facilitating an increase in the oxygen delivering capacity of the conjugated Hb.