Shear cell damage

In capillary shear studies involving M. citrifolia, the extent of cell damage was found to increase with the prevailing level of shear stress (Fig. 2). Trials involving capillary tubes of different lengths yielded similar levels of viability loss at equivalent exposure times, indicating that the death rate is determined by the shear stress alone. 

Since in animal cell culture processes the effects of mechanical stress are much more relevant than in microbial fermentations (Chisti, 1993), it is quite common to adopt scale-up criteria that are associated with cell damage (Joshi et al., 1996), such as constant peripheral impeller velocity, constant aeration rate, and constant integrated shear stress (Croughan et al., 1987). 

A physical protection, mechanism means that the cell resistance to shear remains unchanged, but that the factors that affect the level or frequency of transmitted shear forces to the cell in a given culturing system have changed so that less cell damage is observed... 

Cell damage due to shear forces produced by disintegration of air bubbles Addition of non-ionic detergent may be necessary to prevent foaming, especially in media with a high protein content... 

The provision of a mammal or plant cell culture with aerobic oxygen is as a rule made more difficult by the fact, that, on the one hand, these cells can tolerate hardly any mechanical shear stress (see Section 1.3.5) and, on the other hand, the G/L interface has a cell-damaging effect (damaging of the fold-structure of the proteins). 

The Beall disc valve is a very stenotic valve design. If the assumptions about its in vitro fluid dynamic characteristics are correct, the wall and turbulent shear stress created by this valve could easily damage the endothelial lining of the vessel walls, and cause sublethal and/or lethal damage to blood elements, respectively. In addition, if the red cells were to attach themselves to the Dacron velour cloth covering, the shear stresses adjacent to the valve superstructure would be more than sufficient to cause lethal red cell damage (hemolysis). This has been observed clinically with this prosthesis and the cloth covered Starr-Edwards ball valves. 

Cells can also be eiuiched for enumeration based on their physical characteristics, particularly their size, density, and deformability. For example, many macroscale systems sieve larger CTCs from whole blood by size filtratirm. However, these techniques usually have poor capture efficiency, flow-induced shear may damage cells, and filters are prone to clogging [2], Membranes and microcavities have also been utilized in HIV diagnostics. 

The conclusions in (2) and (3) were further confirmed for TB/C3 hybridoma by Oh et al. (1989, 1992) who used a high shear Rushton turbine with and without gas sparging. Viability studies in the absence of air sparging showed no noticeable cell damage with a maximum power input of 0.25 W/kg. In contrast, relatively low level of aeration resulted in rapid cell death even at much lower impeller power. These results again prove that impeller-induced shear alone does not result in cell death, whereas the presence of gas bubbles results in significant cell death. 

Rapid formation of intracellular and extracellular ice crystals, which leads to mechanical shear forces on cell membranes and organelles causing mechanical cell damage... 

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