5 Ways to Make FACS a More Approachable Topic to Students

Akanksha Saxena

Introduction: FACS

A cell is the most fundamental unit of life, thus making cellular studies one of the most sought-after studies in all the major science fields like immunology, plant biology, pathology, virology and molecular biology. Scientists study cells for several reasons ranging from detecting malignancies to studying necrosis and apoptosis.

While some techniques use only qualitative methods, like observing a specimen using fluorescence microscopy, there is also a need for quantitative estimations. Such a quantitative estimating tool is FACS. FACS is the acronym for fluorescence-activated cell sorting. 

FACS is a special type of flow cytometry. It exploits the science behind “light scattering” and “fluorescence phenomenon” to sort a heterogeneous mixture of cells. As each cell in the mixture possesses a specific light scattering ability and is tagged with a unique fluorescent motif, the FACS machine can sort each one of these cells. 

When students are introduced to the fluorescence phenomenon, they are enthralled to see the variety of vibrant fluorescence colors. As we move ahead in our teaching sessions, we also need to educate them on how to use these phenomena in our labs. FACS is one such example where we use the fluorescence phenomenon to sort cells.

The interdisciplinary approach required to understand FACS is often found missing in most students. Teachers and educators dealing with this topic in conventional classroom setups often sense a feeling of discomfort and difficulty in following the idea of this technique amongst a large proportion of their students. The technique becomes furthermore troublesome and mechanical when the theory of this topic is taught in class. 

Lack of a deeper understanding of how a FACS machine is built, its primary components, the role of underlying systems (fluidics, optics, and electronics), and the art of analyzing FACS data are some topics that students tend to fear a lot. 

Read on to learn more about how you can ease the process of explaining the FACS technique to students in your next class. We try to highlight all the issues encountered by students when dealing with different aspects of this topic. We also list some practical solutions to solve the same. By the end, we’ll convince you why a virtual lab simulation will prove useful not only for your students but also for you as an educator to deliver concepts more efficiently.

3 reasons why FACS can be tricky to teach or learn

There are 3 reasons why students dread the topic of the FACS technique. Acknowledging these issues is the first step toward making the topic more approachable. 

1. Confusion in basics

Students often find it hard to understand the basic functioning of a FACS machine. They are perplexed as to how a technique can sort different types of cells, chromosomes, and other molecules merely based on light scattering and fluorescence phenomena. The basic compilation of the FACS machine is also not clear to most students. They are oblivious to how the concepts of “fluidics, optics, and electronics” cumulatively function in this cell sorting methodology. The different components of a FACS machine and their respective roles are also sometimes not clear to many students.

2. Difficulty in following the steps of the process

Since there are several steps to this technique, teaching them textually might not be an issue for educators but students often find it hard to follow. Understanding the placement of different components in a given order can be difficult to picture for them. “Where do we load the sample”, “how is the excitation laser placed”, “how are the forward-scattered light (FSC) and side-scattered light (SSC) measured”, “how and when is the fluorescent tagging done”, “where is the electronic system placed”, “how does the electronic system convert light signals to electronic signals” and so many more questions come to the students’ minds. The lack of good flowcharts, demonstrative videos and visually engaging tools is sensed as a big problem here.

3. The dearth of demonstrations and visualization tools

Since fluorescence microscopes are expensive, they aren’t always available to students in academic setups. This makes the classes too theoretical with no interesting activity. Students are expected to remember all the details without ever seeing or handling the instrument. This demotivates them to learn the techniques and deprives them of knowing their potential use in their work. Further, there aren’t many video or visual tools at the teacher’s disposal to demonstrate the technique to students. 

5 ways to make FACS a more approachable topic to understand

To address the blocks encountered while teaching the FACS technique, educators can engage the under-listed solutions in their classes. These can clarify many instrumental aspects of the technique and its operation. Not only can they make teaching easier for educators like you but will also make lessons clearer and easier to assimilate for your students.

1. Make the core concepts robust

The first and most important suggestion to educators is to simplify the basics of the FACS technique. You can take charge of one important component at a time and explain its essence in the functioning of a FACS machine. We list a few examples that can be used in the first few classes.

  • Different systems involved in FACS: There are 3 different systems at the interface of which the science of FACS works. They are “fluidics, optics, and electronics”. You should explain why each one of these is important to the working of a FACS machine and how they help in differentiating between different components of a mixture.

  • Different natural phenomena exploited in FACS: The FACS technique exploits the basic science behind “light scattering and fluorescence”. You can explain how these phenomena are observed in the natural world. Further, you can explain how they form part of the optical system of the FACS machine. You can talk in detail about excitation (lasers, lenses) and collection (collection lenses, optical mirrors, optical detectors) optics. You can also choose to explain how a cell/chromosome/molecule interacts with the laser light leading to the emission of rays to the side and the emission of fluorescence signals to the photomultiplier tubes (PMTs). Once students understand this basic flow of steps, you can stress the importance of associated terminologies like forward-scattered light (FSC), side-scattered light (SSC), specificity of the detector (for narrow-range fluorescent dye detection), etc.

FACS machine

Figure: A schematic representation of how FACS works from the FACS simulation by Labster. Full simulation is available for University/College and Professional courses.

FACS optics system

Figure: Optics System of FACS. Image Source

2. Simplify the instrument’s assembly and the role of different parts

The FACS machine is a complex assembly of several components. Educators should devote time to explaining this assembly and the roles of different parts of the machine. The technique and its underlying principle can be made a lot simpler for students if they know how each of the different components comes together in the system. You can readily use the example listed below.

Example: Fluidic System

First, explaining why such a system is in place would be a good idea to begin with. You can explain that the FACS technique isn’t just used for sorting different types of cells, it is also used to study chromosomes (DNA), body fluids, bacteria in the blood and other bodily fluids and other molecules. To deliver the “particle of interest” for its exposure to the optics system (laser), a fluidic system is used. Usually, sheath fluid is used which is a buffered saline solution. The design and shape of the flow chamber are also highly specific and optimized so that the “particle of interest” can easily interact with the laser beam. 

Just like this, you can explain the assembly of optic and electronic systems.

Figure: A snippet from the FACS simulation by Labster showing the flow buffer used for the fluidic system of the FACS machine. Full simulation is available for University/College and Professional courses.

FACS fluidics system

Figure: FACS Fluidic System from Labster’s theory material. Image Source

3. Educate about its real-world applications

Educating your students about the real-world applications of FACS can buzz them with enthusiasm while learning the tough aspects of the subject. This can render them with ideas to utilize the knowledge system they are building today. This is very underrated, yet important advice, as many students in their research know many different techniques but don’t know how and when to utilize them in their research work.

Some of the real-world applications of FACS that are worth mentioning in your next class are:

  • Used in diagnostic, clinical, and pathological labs for various purposes (detection of both benign hematologic processes and malignancies in bodily fluids, monitoring residual diseases, for studying cerebrospinal fluid and bone marrow aspirate) [IMMUNOPHENOTYPING STUDIES].

  • Used for separating the cells of interest from a mixture [CELL SORTING STUDIES].

  • Used for studying DNA replication, identification of DNA content and cells in different stages of replication/cell cycle [CELL CYCLE ANALYSIS].

  • Used for studying multi-drug resistant bacteria in fluid samples [PATHOLOGICAL STUDIES].

  • Used for identification and quantification of immune cells [CELL VIABILITY STUDIES].

4. Use more interactive tools and infographics

The topic of FACS is quite heavy on content. We understand the fear that haunts most students when they have to learn all those intricacies at once. To slash off this misery or at least minimize it, we recommend teachers use more interactive and easy-to-follow infographics, flowcharts, illustrations, and diagrams. 

This can help students visualize how the machine is assembled, how different components work in synchrony, and how one works their experiment using a FACS machine.

facs diagram

Figure: Infographic from Labster. Image Source

5. Use virtual lab simulations

Since FACS is a broad topic with many detailed steps using many unique principles, it can sometimes be difficult to demonstrate all of it in a single class. Even though educators and teachers are passionate about demonstrating the different aspects of a FACS system, they sometimes fall short due to the absence of machines in their labs or the unavailability of videos and illustrations in the public domain. 

We at Labster understand these issues for educators like you. Therefore, we bring virtual laboratory simulations that can ease your process of lecture delivery as well as lab handling sessions. You can make more insightful points as students are rendered with better visual options. The 3D simulations help them better understand the intricacies of operating different types of microscopes. 

Your students don’t have to struggle to imagine different colors of fluorophores as our interactive FACS simulation along with gamification elements, come to the rescue. Using this way of active and immersive teaching, our virtual learning platform takes an advent in the field of Science to make the upcoming scientists thorough with the “basics of their respective subjects”. 


Figure: A snippet from the FACS simulation by Labster showing the virtual setup. Full simulation is available for University/College and Professional courses.

You can learn more about the FACS simulation from Labster or get in touch to find out how you can start using virtual labs with your students.

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