SEPARATION OF CELLS BY SEDIMENTATION

Isopycnic and velocity sedimentation have proved to be broadly applicable techniques for the separation of mammalian cells according to their physical properties, i.e., density and effective diameter. Isopycnic sedimentation has been useful for the determination of the densities of cells; however, isopycnic sedimentation has been less widely applicable than velocity sedimentation for the purification of most kinds of mammalian cells. There are four techniques for velocity sedimentation that have been used by many: elutriation, sedimentation at unit gravity, sedimentation in an isokinetic gradient of Ficoll in tissue culture medium, and sedimentation in a reorienting gradient zonal rotor. All four of these techniques for velocity sedimentation are used with shallow (gm/ml/cm) gradients and are capable of high-resolution separations of cells based on their rates of sedimentation. The kinds of data required for the evaluation of cell separations are discussed. Because of the broad scope of this subject, we have attempted to supply references that will provide specific details that will not fit in this brief review.