流式細胞儀的細胞分流器（cell sorters）：Fluorescence-Activated Cell Sorter (FACS) Magnetic-Activated Cell Sorting (MACS)

 n a cell sorter, especially a

Fluorescence-Activated Cell Sorter (FACS), cells or proteins are separated based on their fluorescence characteristics and other physical properties. Here’s a breakdown of the main technologies involved in the separation:

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🔧 1. Fluorescent Labeling Technology

• How: Cells or proteins are tagged with fluorescent antibodies or dyes that bind specifically to molecules of interest (e.g., CD markers on immune cells).

• Purpose: These tags emit specific wavelengths of light when excited by lasers—allowing identification of cell types or protein expression.

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💡 2. Laser Excitation & Optical Detection

• A laser beam excites the fluorophores.

• Detectors (photomultiplier tubes) capture the emitted light:

  • Forward Scatter (FSC) = Cell size

  • Side Scatter (SSC) = Cell granularity

  • Fluorescence = Specific markers

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⚡ 3. Electrostatic Cell Sorting (Key Separation Tech)

• After detection:

  • The stream of fluid is broken into droplets—ideally one cell per droplet.

  • Each droplet is assigned an electric charge based on fluorescence data.

• The droplets pass through charged deflection plates:

  • Positive charge → deflected to one collection tube.

  • Negative charge → to another.

  • Neutral → to waste.

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🧪 Optional: Magnetic-Activated Cell Sorting (MACS) – Alternate Method

• Uses magnetic beads bound to antibodies instead of fluorescence.

• Cells are passed through a magnetic column:

  • Labeled cells are retained.

  • Unlabeled cells flow through.

• Simpler but less precise than FACS.

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Summary Table:

Technology	Role
Fluorescent antibodies/dyes	Label specific cell markers
Laser and optics	Excite and detect fluorescence signals
Electrostatic deflection	Sort individual cells into tubes
Hydrodynamic focusing	Align cells in single-file