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What is Flow Cytometry and FACS?

Flow cytometry is the measuring (metry) of cells (cyto) as they flow (cells in motion) past a detecting device. The technique of flow cytometry is used to evaluate cells for a number of functions, such as cell counting, phenotyping, cell cycle analysis, and viability.

A flow cytometer uses lasers to create light, which is subsequently dispersed by the sample’s cells, recorded by detectors, and converted into signals for analysis and measurement.

Fluorescence-activated cell sorting (FACS) is a technique to purify specific cell populations based on phenotypes detected by flow cytometry. It analyzes a population of cells on a cell-by-cell basis, a critical capability for today’s researchers and clinicians who are looking for the very few cells among the many cells in a sample (like finding needles in a haystack) that will enable them to study a disease state or biological process. Second, flow cytometry is extraordinarily rapid. Routine sample analysis rates can range up to 10,000 cells per second—an incredible advancement over historical methods of visually examining and counting cells. Finally, flow cytometry has the capacity to simultaneously measure multiple parameters (multiplexing) of single cells. Multiplexing allows researchers and clinicians to gather more information from a single sample faster than ever before. These capabilities have made flow cytometry a powerful tool with multiple applications for researchers and clinicians alike. – BD Biosciences

What are the three systems of Flow Cytometry?

1. Fluidics

Particles are sent in a stream by the fluidics system to the laser beam for analysis.

  • Sheath Fluid: It is typically a buffered saline solution, passes through a flow cytometer in laminar flow.
  • Laminar flow: A flow in which there is minimal to no mixing between the liquid layers as they pass one another.

2. Optics

Lasers are used in the optics system to illuminate the sample stream’s particles, and optical filters are used to guide the generated light signals to the proper detectors. As the cells pass the laser one at a time, their cell structure causes some of the beam to be refracted.

  • Forward Scatter: It’s useful in determining size of the cell. The relative cell size is commonly determined by light scattering past the cell.
  • Side Scatter: It offers information on the complexity of the cell, the nucleus structure and granularity of the cell.

3. Electronics

The electronics system transforms the observed light signals into computer-processable electrical impulses. The electronics system can also start making sorting judgments to charge and deflect particles for some instruments having a sorting capability (FACS).

New to Flow or want to expand your understanding and improve your experiments?  

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