DIELECTROPHORETIC SEPARATION OF MAMMALIAN-CELLS STUDIED BY COMPUTERIZED IMAGE-ANALYSIS

A method was developed for studying the dielectrophoretic properties of both homogeneous and mixed populations of mammalian cells. Computerized image analysis was employed to quantify the rate of motion of cells suspended in low conductivity medium as they moved under the influence of a non-uniform alternating electric field produced by an interdigitated electrode array. As expected for dielectrophoresis, cells collected at highly inhomogeneous electric field regions of the array when the electrical polarizability of cells exceeded that of the suspending medium or away from such regions when their polarizability was less than that of their medium. These two types of behaviour are classified as positive or negative dielectrophoresis respectively, and the cell collection patterns agreed well with those computed for the electrode configuration employed. The dielectrophoretic characteristics of normal, leukaemic, and differentiation-induced leukaemic mouse erythrocytes were measured as a function of frequency in the range 5 x 10(2)-10(5) Hz and were shown to be significantly different. By suitable choices of applied frequency and cell suspension medium, dielectrophoretic separation of different cell types from cell mixtures was demonstrated. The image analysis technique not only allows for rapid characterization of homogeneous cell populations but also permits individual subpopulations to be discriminated within cell mixtures; these are necessary steps for the development of dielectrophoretic separation methodologies for medical and biotechnological applications.