ABSTRACT
Limitations associated with the storage of red blood cells have motivated the development of novel blood substitutes that are able to withstand long-term storage at elevated temperatures. The hemoglobin of the earthworm Lumbricus terrestris (LtEc) is an attractive blood substitute candidate, since it is resistant to oxidation and aggregation during storage. Several factors were investigated to optimize the thermal and oxidative stability of LtEc during storage, including pH, antioxidant supplements, and deoxygenation. A strategy for the reduction of fully oxidized LtEc with antioxidants was also developed. Overall, LtEc was shown to have the highest thermal stability in Ringer's Modified Lactate solution with 10 mM HEPES at pH 7.0. Deoxygenation of the LtEc was also shown to significantly reduce oxidation of the ferrous heme iron (e.g., %Fe2+ after 7 d at 37 °C = 75.7%). However, even in cases where oxidation does occur, the addition of 1.8 mM ascorbic acid (AA) was found to reduce 98.3% of the oxidized LtEc (37 µM heme). Most importantly, the oxygen transport properties of LtEc were unaffected by storage at high temperatures or oxidation followed by reduction with AA. These results show that LtEc can be stored at high temperatures (37 °C) without any significant loss of function.