Lasers for Flow Cytometry

Flow cytometry enables detection and analysis of a variety of cellular properties in a large cell population and is a critical technology for both clinical medicine and basic research in the life sciences. Lasers are used in flow cytometry as the excitation source of fluorophore-labeled cell samples. Often, multiple laser colors are needed in order to characterize multiple cellular properties.

In the cytometry process, a cell population sample labelled with fluorophores is suspended in a fluid and then the cells, one by one, are made to pass through one or more laser beams of different colors at very high speed. The physical and biological properties of the cells are characterized by measuring the scattering effects as well as emitted fluorescence signals. The cells are guided through the laser beams either as a hydro-dynamically focused jet stream or by using microfluidic devices.  The signal data generated is computer processed and usually presented in single-dimension histograms, or in bivariate dot plots to separate out, detect, and quantify different sub-populations of cells in the sample.  More advanced cytometry systems are also able to physically separate and thereby purify cell populations of interest based on their optical properties by use of Fluorescence-Activated Cell Sorting (FACS).