Turbulence cell damage

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. 

Cherry and Papoutsakis (1986, 1988) have shown that these collisions can be an important contributor to cell damage. They defined a turbulence collision severity (TCS), which is a product of the kinetic energy dissipated in collisions and the frequency of collisions, as follows ... 

Water velocity and turbulence can damage protective films and deposits on metal surfaces causing increased corrosion. Soft metals, such as copper, are particularly susceptible to erosion corrosion, but steel and other metals are also susceptible if the water velocity is sufficiently high. The critical velocity for erosion-corrosion of copper in freshwater is about 5 s (1.52 m/s), but this velocity can drop sharply as the chemical corrosivity of the water increases. Suspended solids in the water can increase the erosion characteristics of the water [1]. Deposits can result in accelerated corrosion from the formation of oxygen differential concentration corrosion cells. 

The main reasons for the damage to cells in a reactor are the apparent shear forces and the collision of microcarriers with themselves and with turbulent eddies. In the literature studies are mainly focused on suspension cells and there again on hybridoma cells. The work reported in the hterature can be divided into two fields studies dealing with the influence of various stirrer speeds on cell viability and those investigating the influence of defined shear forces on cells with a viscosimeter. 

Croughan M, Sayre ES fe Wang DIG (1989) Viscous reduction of turbulent damage in animal cell culture. Biotechnology and Bioengineering 33 862-872. 

However, cells grown on solid microcarriers are often subjected to fluid mechanical damages caused by small turbulent eddies as well as by collision between microcarriers and against the impellers and other bioreactor parts. The development of macroporous... 

Turbulent shear stresses are large enough to cause sublethal and/or lethal damage to red cells and platelets thereby reducing their half-1ifes. Therefore, it is not surprising to observe clinically, hemolysis and thromboembolic problems with this prosthesis. 

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