Cell sorting

FACS - fluorescence activated cell sorting

Sort definition:

The ability to select any population, defined by a logical combination of regions, and isolate that population from the sample.

How to sort cells?

The initial processes are the same as for cytometric analysis:

  • hydrodynamic focusing of the cell or particle mixture to form a central core in the fluid coating;
  • passing the cells through the laser beam with subsequent analysis of the scattering and fluorescence signals;
  • using regions and gates to define subpopulations;

Electrostatic sorting: course of events in the sorting chamber?

1) Vibration of the nozzle under the influence of the transducer causes the stream to break down into droplets containing sorted cells / particles;

2) At the interrogation point level (where the laser beam runs), the signal is processed and the decision made: sort to the left, sort to the right, discard;

3) Stream loading: negative charge when the drop goes left; positive when right;

4) Bending of the stream in the electrostatic field created by the deflection plates maintained at high voltage (+/- 5000 V): the charged drops are attracted to the appropriate plates, forming side fluxes;

5) Collecting sorted droplets of fluid containing cells / particles into tubes or onto a plate.