Spray drying has been widely used in food science for long-term storage of products such as powdered milk, and it has recently been used for preservation of more temperature sensitive products such as human blood plasma and single-cell organisms. However, there are no previous reports of successful spray drying of viable mammalian cells. This study lays the groundwork for spray drying of red blood cells (RBCs), with the ultimate goal of creating a blood transfusion product that is stable at room temperature.
To identify promising operating conditions for RBC spray drying, experiments were performed to measure the moisture sorption characteristics of RBCs, as well as their sensitivity to thermal damage. The moisture sorption isotherm of packed RBCs was measured by equilibrating the sample in various relative humidity environments and measuring the residual moisture content. The resulting data was sigmoidal in shape, in agreement with the best-fit Guggenheim–Anderson–de Boer (GAB) model. RBC sensitivity to thermal damage was determined by measuring hemolysis and cell recovery after exposure to temperatures between 37 °C and 80 °C for 25 s. There was no apparent damage for temperatures up to 60 °C, but exposure to temperatures of 70 °C or higher caused complete cell lysis. Together, the results of these experimentsallowed the use of a mathematical model of the spray drying process to identify promising operating conditions.
Based on these model predictions, preliminary RBC spray drying experiments w ere performed using a custom system consisting of a two-fluid atomizer, a drying chamber and a biosafety enclosure with a HEPA filter. The results demonstrate the potential for creation of an RBC powder that is sufficiently dry for long term storage. However, few intact RBCs were observed after rehydration. To improve RBC viability, we suggest that the spray drying system should be modified to enable a secondary gas input and better insulation of the drying chamber.