Chelating agents as possible artificial blood substitutes.

The synthetic cobalt-containing oxygen carriers are briefly reviewed as well as some of the heavier metal systems. The earlier chemistry of the iron complexes with dioxygen is discussed. Some of the more recent results on the reversible binding of oxygen to iron complexes is presented. Initial results showed that low temperatures and steric hindrance in the vicinity of the binding site were important parameters. It is shown further that a rather extensive steric hindrance can yield iron complexes that are efficiently reversible at 25 C. Two such species are known at this date. It is possible that such compounds could act as artificial blood substitutes by attaching to them suitable permanent ligands. Furthermore, solubilization of such species either in fluorocarbon emulsions or by direct covalent attachment to water-soluble polymers offers an opportunity to render them physically compatible with plasma, as substitutes for the red cell.