Effects of cell lysis on the rheological behavior of red blood cell suspensions

Rheological studies of lysed cell suspensions are performed with a magneto acoustic ball microrheometer. Two methods for lysing the cells are developed in order to provide cell volume concentrations identical to control intact cell suspensions. The first uses a freeze-thaw technique and the second uses sonication. It is found that cell suspensions disrupted by sonication have a lower viscosity than intact suspensions, whereas cell suspensions lysed by the freeze-thaw method exhibit a higher viscosity. Sonication is discovered to have a detrimental impact on the cell membrane, and to cause complete destruction of the cell membrane structure. Measurements of the steady state viscosity show that indeed the presence of the membrane is not detected, and that what is measured is mainly the viscosity of the hemoglobin solution. On the other hand, freeze-thaw results indicate that at least two phenomena occur. The first phenomenon, occurring during the first freeze-thaw cycle, produces an increase in viscosity and in viscoelasticity. The second one, taking place after subsequent freeze-thaw cycles, induces a decrease in the bulk rheological properties. Several possible mechanisms are presented to explain the observed phenomena.