Flow cytometry is a biophysical technique where microscopic objects suspended in a fluid are counted, examined and sorted. It is also known as fluorescence-activated cell sorter (FACS). Cells are passed through beam of light, different cells they scatter the light or emit fluorescence helps to identify different cells.
Flow cytometry is based on the principle of hydrodynamic focusing of cells to light excitation source like laser. Cells are labeled with fluorescent reagent and this mixture of cells is passed through small aperture so that to focus each cell which undergoes laser interrogation.
The emission of light or fluorescence provides particle properties, the signal is detected by fluorescence detector and electric charge is applied accordingly. The cells finally reach the electric plates, where according to their charge they are sorted into separate beaker. This helps to provide quantitative and qualitative information about fluorochrome-labeled cell surface receptors and intracellular molecules like DNA and cytokines. Light scattering by the particles gives information of particle’s size and granular content of particle.
The characteristic feature of flow cytometry is it measures fluorescence per cell. The major application of flow cytometry is in cell sorting i.e. separation of subpopulations of cell which are of interest from other population. Electrostatic deflection method is generally used for cell sorting.
Flow cytometry has various applications like in separation of different types of cells which bears characteristic proteins and binds to monoclonal antibodies specific to protein. Measurement of density of particular antigen. It is also used in the measurement of cells DNA and RNA content and for its general shape and size assessment.