What Is FACS?

March 2020


Fluorescence-activated cell sorting (FACS), sometimes called fluorescence-assisted cell sorting, is a specialized type of flow cytometry that uses fluorescent markers to target and isolate cell groups. It is commonly used in hematopoiesis, oncology, and stem cell biology research.

How Does Fluorescence-Activated Cell Sorting Work?

FACS technology separates cells based on cell surface markers. Antigenic ligands, such as proteins and carbohydrates, give each cell a unique surface phenotype, and specific antibodies associated with the cell surface antigens are then used to target cells with those antigens.

Let’s do a deep dive:

  • An antibody matched with an antigen on the surface of the targeted cell is labeled with a fluorescent molecule and mixed into the cell sample
  • One by one, the cells are passed in a continuous flow through a laser beam
  • Each cell scatters some of the laser light, and cells tagged with the identifying antibody emit a fluorescent light
  • Cells are deposited into containers based on their fluorescence or specific light scattering pattern

Cells can be separated by fluorescence or by scattered light, either a forward (parallel) scatter that indicates cell size or a side (perpendicular) scatter that indicates granularity.

FACS Analysis: What Are the Advantages and Disadvantages?

With the ability to separate cells based on surface markers as well as physical characteristics like size, granularity, and cytokine expression, FACS technology is highly versatile. It also has a high throughput, and FACS is now the standard in many clinical and research labs.

However, there are some disadvantages to FACS, such as speed. The FACS sorting process is slow; a rapid stream flow rate makes it difficult to properly identify cells, so the stream flow rate must be maintained at a reasonable sorting speed. Additionally, as a positive selection process, FACS requires starting with a high number of cells. Recovery rates average between 50 and 70 percent, which is a disadvantage when working with rare cells.

FACS poses a hidden challenge, too: The technology is expensive, and it requires highly skilled personnel to use and maintain.

So, what is the alternative to FACS?

How Do Akadeum Microbubbles Compare to FACS Technology?

Akadeum buoyancy-activated cell sorting (BACS™) microbubbles are an alternative to traditional cell isolation methods like FACS technology. Our microbubbles capture target cells and quickly float them to the surface of a biological sample for removal.

Time? No worries. BACS™ microbubble technology is easy to use and significantly reduces cell sorting time. The entire process takes about 30 minutes for a typical negative selection kit or less than 10 minutes (!) for Akadeum’s depletion kit.

Equipment costs? Forget ‘em. No additional equipment is needed to use our microbubbles, reducing the cost of purchasing and storing magnets, columns, or other expensive materials.

Purity? We’ve got you covered. Microbubbles allow targeted cells to be isolated to a high level of purity—up to 95%.

Check out our line of microbubble cell separation products today.