Dry storage of liposome-encapsulated hemoglobin: a blood substitute

We have previously demonstrated the stabilization of liposome-encapsulated hemoglobin (LEH) by lyophilization (Cryobiology 25, 277-284, 1988). In the present report, we examine the structural and functional recovery of LEH after 3 months in the dry state. We have investigated the incorporation of the protective carbohydrate trehalose in the production and preservation of lyophilized LEH. Vesicle size, retention of entrapped hemoglobin, oxygen-carrying capacity, and percentage methemoglobin were measured as a function of time stored in the dry state under vacuum at room temperature. The results indicate that 150-300 mM trehalose maintains LEH dry preparations with little change in their size or functional characteristics after 3 months in the dry state. These results are compared to those of LEH that has been stored hydrated at 4 degrees C for the same time period.