Flow Cytometry: Scattering Light to Measure Cells

Scientists analyze and quantify characteristics of cells and other particles with the power of lasers.

Shelby Bradford, PhD
| 2 min read

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A high-throughput, single-cell method enables researchers to assess several cell parameters simultaneously with the help of lasers.

Infographic showing how flow cytometry enables researchers to assess several cell parameters simultaneously at a single-cell level with the help of lasers.

(1) Sample Uptake

Scientists prepare samples as single cell suspensions and labels components of interest with fluorescent antibodies or other probes. The cytometer uses pumps to draw the sample through tubing to analyze it.

(2) Cellular Alignment

Using hydrodynamic focusing the instrument injects the sample into a fast-moving stream of fluid that funnels the sample single file through a narrow channel.

(3) Laser Interrogation

The channel leads to a point where the individual cells intersect with one or more lasers. The measured sample is deposited into a waste receptable after it passes this point.

(4) Light Scatter and Detection

As a cell begins to cross the laser beam, it scatters light. Light that mostly crosses the cell is detected as forward scatter and measures the cell’s size. Light that encounters obstacles in the cell changes direction and is detected by a side scatter detector, indicating the granularity of the cell. If the lasers excite fluorescent molecules in the cell, the emitted light is channeled through dichroic mirrors and bandpass filters to isolate specific wavelengths that meet detectors specific for those wavelengths.

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Meet the Author

  • Shelby Bradford, PhD

    Shelby Bradford, PhD

    Shelby is an assistant editor for The Scientist. She earned her PhD from West Virginia University in immunology and microbiology and completed an AAAS Mass Media fellowship.

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