Cell sorting facs machine

FACS (Fluorescence-Activated Cell Sorting) is a flow cytometry technique that individually separates live cells based on fluorescent markers, essential in immunological and cancer research.

About this subject

FACS, which stands for Fluorescence-Activated Cell Sorting, is a flow cytometry technology that physically separates live cells into homogeneous populations. The process uses a laser to excite fluorescent markers attached to antibodies or proteins on the cell surface. Each cell is encapsulated in an electrically charged droplet and deflected by electric fields into distinct collection tubes, achieving purities exceeding 99%.

Developed by Leonard Herzenberg at Stanford University in the 1960s, FACS revolutionized immunology by enabling the purification of cell subtypes such as CD4+ and CD8+ T lymphocytes. Today, machines like the BD FACSAria or Sony SH800 are widely used in research labs and clinics for applications ranging from stem cell characterization to engineering CAR-T cells for cancer therapy.

In addition to sorting, FACS quantifies multiple parameters per cell, such as size (FSC) and granularity (SSC), combined with up to 18 or more simultaneous fluorescence signals. This allows complex phenotypic analysis of heterogeneous samples like peripheral blood or tumor suspensions. The technique requires trained cytometrists and strict quality control to avoid cell damage and ensure reproducible results.

Interestingly, FACS is one of the few technologies that can sort and collect individual live cells for subsequent culture or functional assays, differing from analytical flow cytometry which only measures and discards samples. The high cost of instruments (hundreds of thousands of dollars) is justified by their precision and versatility, making them indispensable in cell and molecular biology.

• Source: BD Biosciences, Stanford University
• Applications: Immunophenotyping, isolation of rare cells, selection of transgenic clones

Frequently Asked Questions

What is the difference between FACS and regular flow cytometry?

Regular flow cytometry only analyzes and measures cells, discarding them. FACS physically separates cells into pure populations, allowing live collection for further experiments.

Can FACS damage cells?

Yes, the process can cause cellular stress due to pressure, laser, and electric fields. However, adjustments such as larger nozzle diameters and low pressure minimize damage, maintaining viability above 90% for most cells.

What fluorescent markers are used in FACS?

Common fluorochromes include FITC, PE, APC, PerCP, and Pacific Blue, conjugated to specific antibodies. Selection depends on laser excitation and the need for multiplexing.