Cellular response to agitation characterized by energy dissipation at the impeller tip

Sf9 insect cells in suspension show an increase in intracellular calcium concentration as a function of local energy dissipation rate in two fluid systems. A significant calcium response (more than a 10% increase) resulted at a dissipation rate above 10(7) cm(2) s(-3) in 15 min capillary flow experiments. Similar results were obtained after 4h with a dissipation rate above 10(5) cm(2) s(-3) or in a bioreactor stirred at greater than or equal to 280 rpm for 4 h with a 6-bladed Rushton impeller. This impeller speed produces a local energy dissipation rate of 10(5) cm(2) s(-3) if the dissipation rate is estimated using the volume of the trailing vortices as the dissipation volume (V = 0.075d(i)(3)). Our results show the capillary flow system to be a good model for prediction of cell damage in a stirred bioreactor.