DIELECTRIC-SPECTROSCOPY OF MAMMALIAN-CELLS .1. EVALUATION OF THE BIOMASS OF HELA-CELL AND CHO-CELL IN SUSPENSION BY LOW-FREQUENCY DIELECTRIC-SPECTROSCOPY

The capacitance of suspensions of CHO and HeLa cells (0.5-3 x 10(6) ce lls/ml) has been measured between 0.2 and 10 MHz. As frequencies decre ase, there is a continuous increase in capacitance of both the cell su spension and the spent growth medium free of cells, a phenomenon which is partially attributed to an increased polarisation of the electrode s. At a given frequency, subtraction of the capacitance of the spent m edium from that of the cell suspension allows one to determine the cap acitance of the cells only. The intensity of this signal varies linear ly with the biomass and cell size. At low frequencies such as those us ed in this study (0.25 MHz), where sensitivity is the highest, concent rations as low as 0.5 x 10(6) cells/ml can be accurately measured. Sug gestions are made how to make these measures on-line, non-invasive and in real time.