Stability test

RBC stability

To perform a stability test for RBC, the cells are considerably deformed by a, user defined, high shear stress for a certain time period. The effect on the cells can be followed, either during the stress application period by the intermittent measurements of their deformability at a fixed shear rate, or by the measurement of a complete deformation curve before and after stress application. Thus, the same LORCA geometry as given in Figure 1 is used for both applying the shear stress and analyzing the result of it.

Monitoring the decrease of RBC deformability is, compared to hemolysis, an early indication of shear induced cell damage (REF Sung Sik Lee).

RBC membrane stability

Using the Ektacytometer, Chasis et al. found that the continuous high shear stress slowly changes the mechanical properties of resealed erythrocyte membranes. (Reference 11 Chasis J.A., Mohandas N., Erythocyte membrane deformability and stability: two distinct membrane properties that are independently regulated by skeletal protein associations, J. Cell Biol., vol. 103:(2), pp. 343-350, 1986.) This causes the cell membranes to fragment progressively. The process can be accelerated by further increasing the applied shear stress. The diffraction pattern gradually looses its ellipticity, and hence EI decreases, under continued high shear stress (see Figure 3). The decrease in EI can be explained by the appearance of randomly oriented cell fragments which add a circular component to the –initially- elliptical diffraction pattern. A similar effect was observed, using the LORCA, in mixtures of rigid and normal deforming RBC, both in the experimental (REF) and clinical situation, e.g. in the blood from patients with sickle cell disease (REF). However, for comparison of results obtained by the Ektacytometer with those of the LORCA it should be kept in mind that the Ektacytometer uses a different method to analyse the obtained diffraction pattern, i.e. 4 diodes detecting light intensity, in contrast to LORCA`s modern digital image analysis.