Flow cytometry (FCM) is a technique used to detect and measure physical and chemical characteristics of a population of cells or particles.In this process, a sample containing cells or particles is suspended in a fluid and injected into the flow cytometer instrument. The sample is focused to ideally flow one cell at a time through a laser beam, where the light scattered is characteristic to the cells and their components. Cells are often labeled with fluorescent markers so light is absorbed and then emitted in a band of wavelengths. Tens of thousands of cells can be quickly examined and the data gathered are processed by a computer.A flow cytometry analyzer is an instrument that provides quantifiable data from a sample. Other instruments using flow cytometry include cell sorters which physically separate and thereby purify cells of interest based on their optical properties.

Flow cytometry is routinely used in basic research, clinical practice, and clinical trials. Uses for flow cytometry include:

• Cell counting
• Cell sorting
• Determining cell characteristics and function
• Detecting microorganisms
• Biomarker detection
• Protein engineering detection
• Diagnosis of health disorders such as blood cancers

APPLICATION

The technology has applications in a number of fields, including molecular biology, pathology, immunology, virology, plant biology and marine biology. It has broad application in medicine especially in transplantation, hematology, tumor immunology and chemotherapy, prenatal diagnosis, genetics and sperm sorting for sex preselection. Flow cytometry is widely applied to detect sperm cells abnormality associated with DNA fragmentation in male fertility assays. Also, it is extensively used in research for the detection of DNA damage,caspase cleavage and apoptosis. Photoacoustic flow cytometry is used in the study of multi-drug-resistant bacteria (most commonly MRSA) to detect, differentiate, and quantify bacteria in the blood marked with dyed bacteriophages.In neuroscience, co-expression of cell surface and intracellular antigens can also be analyzed.In marine biology, the autofluorescent properties of photosynthetic plankton can be exploited by flow cytometry in order to characterise abundance and community structure. In microbiology, it can be used to screen and sort transposon mutant libraries constructed with a GFP-encoding transposon (TnMHA), or to assess viability.In protein engineering, flow cytometry is used in conjunction with yeast display and bacterial display to identify cell surface-displayed protein variants with desired properties. The main advantages of flow cytometry over histology and IHC is the possibility to precisely measure the quantities of antigens and the possibility to stain each cell with multiple antibodies-fluorophores, in current laboratories around 10 antibodies can be bound to each cell. This is much less than mass cytometer where up to 40 can be currently measured, but at a higher price and a slower pace.Flow cytometry protocols used for research often needs validation because of the risk of antibody binding to Fc receptors.