BIOLOGICAL DIELECTROPHORESIS: THE BEHAVIOR OF LONE CELLS IN A NONUNIFORM ELECTRIC FIELD *

One of the recently developed physical techniques applicable to problems of biological interest is dielectrophoresis, which is the motion produced by the action of a nonuniform electric field that acts on neutral particles. With this technique, one can analyze and separate various living cells and organelles suspended in an aqueous medium. The technique for handling numerous cells simultaneously has been described e l ~ e w h e r e . ~ ~ O . ~ ~ The theory for the effect in biological circumstances has been derived and found to be consonant with experimentation in several systems.11.12 Experiments by Mason and T ~ w n s l e y ~ ~ proved singularly successful in separating even closely similar cells, namely, yeast cells that differed only by having been grown on two different media. Chloroplasts have been studied by Ting and associates5 The above-mentioned experiments all involved the treatment of rather large numbers of cells a t once. We shall report on the application of the technique to the study of single cells, one a t a time. The method is simple and direct. The force exerted by a nonuniform electric field is induced to act in a direction that opposes that of gravity. At balance, the magnitude of the field provides a measure of the polarizability of the individual cell. In this fashion, cells from a mixed population can be studied separately.