AUTOMATED CELL SORTING WITH FLOW SYSTEMS

Abstract

The major successes of biochemistry and molular biology have derived from the isolation and characterization of macromolecules from complex solutions and structures. The analogous requirement in the field of cellular biology is for the preparation of pure populations of cells from organs and tissue culture. This ob jec­ tive is of primary importance in basic research of cellular differentiation and regula­ tion, as well as in applied areas such as clinical diagnosis and treatment. The same considerations apply to subcellular structures that extend from organelles or chromosomes to the ultimate structural limit of individual molecules, thereby bridging the gap with solution biochemistry. Cell separation is not a new problem nor has it been neglected in the past. Numerous methods exist for the bulk isolation of cells, including, for example, sedimentation, electrophoresis, or phase partitioning (134). In many instances, however, these methods lack sufficient selectivity. The techniques of automated cell analysis and sorting discussed here deal with the problem of heterogeneity by examining individual cells dispersed in suspension. Thus, the distributions of physical, structural, and functional properties of the population can be assessed and coupled in a logical manner with the sorting of desired cells for morphological examination or biologicallbioch emical studies. The flow systems designed for this purpose are capable of high speed (currently up to lOLI05 cells/sec) and a selectiv­ ity limited only by the nature of the reagents and physical signals used to differenti­ ate between the cellular subpopulations. In many instances, the sorting procedure can be carried out under conditions that insure preservation of viability and sterility. In fact, by eliminating debris and dead cells, overall viability can actually be increased. The duality of analysis and sorting cannot be overstressed. Although many flow instruments exist for analytical purposes alone and are of great utility. the