Effects of the hydrodynamic environment and shear protectants on survival of erythrocytes in suspension.

Survival of media-suspended porcine erythrocytes exposed to various hydrodynamic environments was investigated with and without such shear protectant additives as bovine serum albumin, dextran and the non-ionic surfactant Pluronic F68. Erythrocytes provided a model cell population with cells of a uniform size, metabolic state and shear tolerance. Because the cells were non-growing, any shear adaptation effects were avoided. Cell lysis was followed by microscopic counts or release of haemoglobin. The cells were susceptible to agitation damage in unaerated shake flasks agitated at 100 rpm or greater. Relative to additives-free operation, the presence of 0.1% (w/v) dextran or albumin prolonged cell survival, but Pluronic F68 actually enhanced cell lysis in flasks agitated at 100 rpm. The protective effect of the additives depended on the hydrodynamic conditions. The protective effect of albumin was demonstrated also in aerated conditions in a split-cylinder airlift bioreactor (aspect ratio of 8.8; riser-to-downcomer cross-sectional area ratio of 1.0; specific power input of 0.34 W m-3). Comparison of the cell lysis characteristics in the airlift device and the best case performance of the shake flask showed longer survival in the flask (100 rpm); however, the length of survival in the reactor (approx. 70 h) was sufficient for practical purposes. In all cases, the cell lysis pattern conformed initially to zero-order dependence in cell concentration, becoming first-order after varying degrees of exposure to hydrodynamic forces. Fatigue failure of cells was inferred.