Scientific Publications by FDA Staff

Biotechnol Prog 2011 Jul;27(4):1172-84

Synthesis, biophysical properties, and oxygenation potential of variable molecular weight glutaraldehyde-polymerized bovine hemoglobins with low and high oxygen affinity.

Zhou Y, Jia Y, Buehler PW, Chen G, Cabrales P, Palmer AF

In a recent study, ultrahigh molecular weight (M(w) ) glutaraldehyde-polymerized bovine hemoglobins (PolybHbs) were synthesized with low O(2) affinity and exhibited no vasoactivity and a slight degree of hypertension in a 10% top-load model.(1) In this work, we systematically investigated the effect of varying the glutaraldehyde to hemoglobin (G:Hb) molar ratio on the biophysical properties of PolybHb polymerized in either the low or high O(2) affinity state. Our results showed that the M(w) of the resulting PolybHbs increased with increasing G:Hb molar ratio. For low O(2) affinity PolybHbs, increasing the G:Hb molar ratio reduced the O(2) affinity and CO association rate constants in comparison to bovine hemoglobin (bHb). In contrast for high O(2) affinity PolybHbs, increasing the G:Hb molar ratio led to increased O(2) affinity and significantly increased the CO association rate constants compared to unmodified bHb and low O(2) affinity PolybHbs. The methemoglobin level and NO dioxygenation rate constants were insensitive to the G:Hb molar ratio. However, all PolybHbs displayed higher viscosities compared to unmodified bHb and whole blood, which also increased with increasing G:Hb molar ratio. In contrast, the colloid osmotic pressure of PolybHbs decreased with increasing G:Hb molar ratio. To preliminarily evaluate the ability of low and high O(2) affinity PolybHbs to potentially oxygenate tissues in vivo, an O(2) transport model was used to simulate O(2) transport in a hepatic hollow fiber (HF) bioreactor. It was observed that low O(2) affinity PolybHbs oxygenated the bioreactor better than high O(2) affinity PolybHbs. This result points to the suitability of low O(2) affinity PolybHbs for use in tissue engineering and transfusion medicine. Taken together, our results show the quantitative effect of varying the oxygen saturation of bHb and G:Hb molar ratio on the biophysical properties of PolybHbs and their ability to oxygenate a hepatic HF bioreactor. We suggest that the information gained from this study can be used to guide the design of the next generation of hemoglobin-based oxygen carriers (HBOCs) for use in tissue engineering and transfusion medicine applications.