Fluorescence-activated cell sorting (FACS), sometimes called fluorescence-assisted cell sorting, is a specialized type of flow cytometry that uses fluorescent markers to target and isolate cell groups. This cell sorting technique is commonly used in hematopoiesis, oncology, and stem cell biology research.
Fluorescence-activated cell sorting (FACS) is a specialized type of flow cytometry. It provides a method for sorting a heterogeneous mixture of biological cells into two or more containers, one cell at a time, based upon the specific light scattering and fluorescent characteristics of each cell.
FACS (fluorescence activated cell sorting) differs from conventional flow cytometry in that it allows for the physical separation, and subsequent collection, of single cells or cell populations. FACS is useful for applications such as establishing cell lines carrying a transgene, enriching for cells in a specific cell cycle phase, or studying the transcriptome, or genome, or proteome, of a whole population on a single cell level.
The system is adjusted so that there is a low probability of more than one cell per droplet. Just before the stream breaks into droplets, the flow passes through a fluorescence measuring station where the fluorescent character of interest of each cell is measured. An electrical charging ring is placed just at the point where the stream breaks into droplets. A charge is placed on the ring based on the immediately prior fluorescence intensity measurement, and the opposite charge is trapped on the droplet as it breaks from the stream. The charged droplets then fall through an electrostatic deflection system that diverts droplets into containers based upon their charge. In some systems, the charge is applied directly to the stream, and the droplet breaking off retains charge of the same sign as the stream. The stream is then returned to neutral after the droplet breaks off
A fluorescence-activated cell sorter (FACS)
An antibody specific for a particular cell surface protein is associated to a fluorescent molecule and then added to a mixture of cells. For fluorescence when the specific cells pass through a laser beam they are monitored. Droplets containing single cells are given a positive or negative charge, based on whether the cell has limited the fluorescently-tagged antibody or not. Droplets containing a single cell are then detected by an electric field into collection tubes according to their charge.