Fluoresence activated cell sorting is a particular form of flow cytometry that enables a mixture of different cells to be sorted one by one into one or more containers. The cells are sorted according to their specific light scattering and fluorescent characteristics.
In a complex mixture of biological cells, there may be more than one type of cell that have different antigenic and other markers on their surface. These markers can be tagged using fluorescent labels. As these cells pass a laser, the labels or fluorophores are excited and emit light at longer wavelengths than the laser beam. This can be picked up by detectors, which are then able to sort the cells according to their specific light scattering and fluorescent characteristics.
The cells are passed into the middle of a fast flowing liquid stream, which is arranged to ensure the cells are well separated. Vibration is applied to break the stream up into droplets in such a way that one cell is present per droplet. Just before the stream becomes droplets, it is passed through a system that measures the fluorescent feature of each cell. Then, an electrical charging ring is positioned in the stream at the point immediately before it breaks into droplets. The ring is charged according to the fluorescence intensity just measured. The opposite charge is trapped on the droplet as it separates from the stream. These charged droplets fall through an electrostatic deflection system that separates them into different containers according to their charge.
Flow cytometry using fluorescent-based segregation and counting is a useful scientific instrument since it can provide fast and accurate quantitative recording of the fluorescent signals from each individual cell.
The first fluoresence-based device was the ICP 11 which was developed in 1968 by Wolfgang Göhde from the University of Münster. It became available commercially in 1968 and 1969 when it was manufactured by the German developer Partec through Phywe AG in Göttingen.