The possibility of using human blood for transfusion is limited by requirements of blood-typing, the danger of transmitting certain diseases, and a short shelf life of liquid blood. These limitations and the wide range of applications of blood substitutes have fueled a worldwide search for safe, effective, and universal blood substitute materials.

One major route to avoid the problems associated with blood (i.e., AIDS, Hepatitis, etc.) involves the use of isolated human hemoglobin (Hb) because of its high capacity of oxygen and hemocompatibility. However, cell-free Hb has to be either molecularly modified or encapsulated in order to prevent its dissociation into dimers, decrease the high oxygen affinity, and increase the retention time in circulation. This route of research requires the use of specifically designed cross-linker reagents necessary to modify the Hb protein.

With molecular engineering techniques, a new family of cross-linking reagents was developed, based on nicotinamide-adenine dinucleotide (NAD) derivatives. One of the reagents designed, namely oxidized beta-NAD (o-NAD), was reacted with deoxyHb to produce NAD-derivatized hemoglobin (HbNAD). The latter was further polymerized to yield poly-HbNAD.

Macroscopic properties of HbNAD and poly-HbNAD were studied. From the results obtained, it is evident that poly-HbNAD possesses a physiological oxygen-carrying capacity and oncotic characteristics similar to whole blood. These properties make poly-HbNAD a viable potential candidate as a resuscitation fluid.