Dielectrophoretic forces can be safely used to retain viable cells in perfusion cultures of animal cells

Dielectrophoresis is a well established and effective means for the manipulation of viable cells. However, its effectiveness greatly depends upon the utilization of very low electrical conductivity media. High conductivity media, as in the case of cell culture media, result only in the induction of weaker repulsive forces (negative dielectrophoresis) and excessive medium heating. A dielectrophoresis-based cell separation device (DEP-filter) has been recently developed for perfusion cultures that successfully overcomes these obstacles and provides a very high degree of viable cell separation while most of the nonviable cells are removed from the bioreactor by the effluent stream. The latter results in high viabilities throughout the culture period and minimization of lysed cell proteases in the bioreactor. However, an important question that remains to be answered is whether we have any adverse effects by exposing the cultured cells to high frequency electric fields for extended periods of time. A special chamber was constructed to quantitate the effect under several operational conditions. Cell growth, glucose uptake, lactate and monoclonal antibody production data suggest that there is no appreciable effect and hence, operation over long periods of time of the DEP-filter should not have any adverse effect on the cultured cells.