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Flow Cytometry

The CS&T Report: Its Troubles, and How to Fix Them

What is one of the first steps of the flow cytometer start-up routine? To check if the cytometer is in good shape, of course! Everyone wants to run on a reliable instrument, and assessing the daily performance of the instrument show us its behaviour over time and allows us to react fast in case of…

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An Introduction to Alexa Dyes

Long before “Alexa” was a household name, Alexa dyes were an established series of fluorescent dyes. The inventor Richard Paul Haugland named the dyes after his son Alex. Originally a trademark of Molecular Probes, the Alexa family is now a part of Thermo Fisher Scientific. Alexa dyes are frequently used as labels in fluorescence microscopy,…

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3 Ways to Use Flow Cytometry for Your Activation Experiment

Studying immune cell activation allows scientists to understand the way the body mounts a response to a specific infection, autoimmune diseases, or cancer. This knowledge plays a direct role in developing more efficacious vaccines and therapies. When tasked with capturing information on immune cell activation, flow cytometry remains the gold standard due to its versatility,…

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How to Unclog Your Flow Cytometer

Welcome back, fellow flow cytometry friend! I am sure that you are rocking your data acquisition at this point, having perfected your understanding of panel setup, fluorophore usage, and using the flow cytometer of your choice. However, with as many samples as you are running, it is possible that you may be experiencing a little…

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Five Things That Irritate Flow Cytometrists

I have worked in flow cytometry for a number of years. I’m still annoyed that many myths and imprecisions are perpetrated and perpetuated. Here is my non-exhaustive list of cytometry-related beliefs that send flow cytometrists screaming from the room or at least, being English, make me tut sadly. Forward Scatter Equals Cell Size No No…

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Post-sorting Checks and Measures

In my previous article I discussed steps you can implement to ensure that a sample is ready for cell sorting. But now it’s time to make sure the sort worked. Here are a few sorting checks and measures to ensure that all’s well that ends well. Post-sorting Checks and Measures Re-evaluate Your Catch Tubes Sorting…

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Guidelines for Efficient Cell Sorting – Part 1

Flow cytometry is a pervasive tool to characterize just about anything in cell biology. From quantifying the expression of surface antigens, to determining the physiological changes in cells and everything in between, flow cytometry is as indispensable to a cell biologist as a knife is to a surgeon. Cell sorting is pivotal in enabling researchers…

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Sheath Pressure: Nozzle Size Does Matter

Hello again, fellow Flow Cytometry Fan! It looks like you have your experiment all planned out, including staining protocols and gating schemes, and are ready to get some paradigm-shifting data. But before we start “plugging-and-chugging” samples through your cytometer of choice, we need to make sure that the nozzle size and sheath pressure are set…

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The 3 Most Common Flow Cytometry Fallacies

Flow cytometry is fast evolving from a method only revered by immunologists, to one used by nearly every biological specialty. It’s pretty much my favorite tool. Unfortunately, as with most lab techniques, much of flow cytometry is taught on the job without a lot of standards. And too often bad habits are passed along like…

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Chromosome Analysis by Flow Cytometry

In most people’s minds a flow cytometer can sort, view and count cells e.g. lymphocytes, thymocytes, cultured cells and even non-mammalian cells such as yeast or bacteria. However, in reality, a flow cytometer is capable of providing information about any particle as long as it has detectable fluorescence. This fluorescence may occur either inherently or…

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Are Quantum Dots Any Good for Flow Cytometry?

What Are Quantum Dots? Quantum dots were discovered in the early 1980s. However, it was not until the late 1990s that their use in biological applications was suggested.1 Quantum dots are semiconducting nanocrystals made of artificial atom clusters. Their size generally ranges from 2 to 20 nm. Size is crucial for their physical properties because…

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The Difference Between an Image, Flow, Time-lapse and Cell-sorting Cytometer

Ah, cell counting — it’s the oldest trick in the book! Well, not really, but people have been developing methods for counting cells since the late 1800s. It has been around for a while. But what different methodologies are available to biologists now? Well, hold on, because you’re in for a treat! In this article, we…

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Hierarchical or Boolean Gating: Which One to Choose?

A flow cytometer collects the events you are interested in, and also ‘sees’ every event that goes through. This includes debris and even bits in your buffers. As cytometrists, we gate our cells to exclude unwanted bits and to focus on the sub-populations that we are interested in studying. There are two main ways of gating…

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How Fluorescent Molecules Work

Fluorescence is one of the most important and useful tools in a biologist’s toolbox. In biology, nearly every field, from physiology to immunology, uses fluorescent molecules (aka fluorophores) to detect proteins. However, the specific science behind how fluorescence works can be confusing or overlooked. Have no fear! In this article, we break down key points of…

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Hydrodynamic Focusing in Flow Cytometry

If you have sorted samples or phenotyped cells by surface expression of proteins, you’ve probably wondered how each cell is sorted or phenotyped in a flow cytometer? This question seems trivial, but in reality it took a while for engineers to figure it out. Before I get into today’s topic on “hydrodynamic focusing,” I’ll walk…

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Multiplex Cytometric Bead Array: The ABCs of CBAs

Multi-parameter data acquisition is key to the modern era of science research. I, for one, wish every single experiment that I design would give me the maximum amount of information. For example, in cell biology and immunology, we want to capture as much information (be it cytokines/hormones/chemokines) as possible about a given cell population. Of…

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Demystifying the Flow Cytometry Optics System: A Peek Under the Hood

To many users, the flow cytometer is a magic box: put in cells, get out data. You click the button to tell it which colors to look at without much thought about how the machine does this. However, not all fluorophores are created equal—some configurations might exclude the spectrum you’re really looking for. Here’s a…

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The History and Future of Fluorescent Labels: We’ve Come a Long Way, Baby!

If you’ve been keeping up with our recent series of articles, welcome back! If not, you can catch up on how fluorescence works or what not to do with your flow experiment. In short, we have been discussing fluorescent labels and their role in flow cytometry. Today, I’ll round out our discussion by touching on…

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Corralling Your Cells: How to Gate in Flow Cytometry

Flow cytometry. Some people love it—most hate it—but all can agree that it is one of the most powerful analytical tools immunologists possess. Here’s a quick refresher: as the name suggests, flow cytometry measures the physical and chemical characteristics of cells. This is accomplished by fluorescently labeling cell surface markers/proteins using antibodies conjugated to fluorophores.…

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Lighting the Way: Understanding Flow Cytometry Fluorophores

As science is becoming more interdisciplinary, the tools we use to answer questions are also crossing party lines. Case in point: flow cytometry. Once a tool only used by “real” immunologists, flow cytometry is fast becoming a method by which numerous questions can be answered, from the length of a cell’s telomeres, to the state…

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Analyzing Cell Signaling with Flow Cytometry: Go with the Flow

Phosphorylation Equals Cell Signaling! How do cells communicate and respond to their environmental cues? This question has been on the hot list for scientists ever since the discovery of the cell. Cells use signaling cascades based on biochemical reactions to deliver or receive messages. How cool is that? The major secret of cell signaling was…

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Detection of Apoptosis by Flow Cytometry: To Be or Not to Be

Sometimes only a small subset of a cell population will show apoptotic features making flow cytometry an excellent way to identify and quantify them. A previous Bitesize Bio article showed how flow cytometry can detect apoptotic hallmarks. More than 30 different dyes can be used to detect apoptosis. It is also true to say that…

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Cell Cycle Analysis by Flow: DNA Stains and Beyond

While you can observe mitotic cell cycle progression using immunofluorescence, flow cytometry is a great tool to delineate details that aren’t apparent by chromosomal morphology alone. DNA stains are a great way to get a general idea of what your cells are up to. There are also a number of other stains you can use…

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Flow Cytometric Apoptosis Assays for Cell Death

Apoptosis, often called programmed cell death, is a carefully regulated process that is part of normal development and homeostasis. Apoptosis is morphologically and biochemically distinct from necrosis, which is conversely called accidental cell death. Dysregulation of apoptosis is implicated in disease states such as cancer, autoimmune disease and degenerative conditions. Apoptosis consists of an orderly…

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Top 5 Tricks for Using FlowJo

Are you planning to do cellular immunology research?  Then chances are you will be introduced to the flow cytometer –  “a modern immunologist’s best friend.” This modern magic box is a highly versatile machine packed with cutting-edge fluidics and photonics (lasers). Combined with the monoclonal antibodies conjugated to fluorochromes capable of emitting light signals from a…

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Ensure Reproducibility: Control for Lot-to-Lot Variation of Antibodies

When starting a long-term experiment, you need to take a lot of things into consideration (availability of cells, reagents, planning time points), but do you ever think about your antibodies? If you buy an antibody from a manufacturer, run out half way through the study, and buy the same antibody again, have you thought about…

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Introducing CyTOF: Cytometry of the Masses

Flow cytometry remains unparalleled as a single-cell analysis technology.  The ability to analyze 14 or more fluorescent parameters on a million cells or more allows for detailed understanding of complex biological processes. The Problem With Traditional Flow Cytometry One limitation of flow cytometry is the reliance on fluorescent tags.   Even with careful panel design, loss…

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Mass(ively powerful) Cytometry

Mass Cytometry is a relatively new technology which has recently featured in many high-impact journals. You may have read about instruments including the CyTOF, CyTOF2, and more recently, the Helios. With these instruments becoming more widespread, you might find yourself asking, what is mass cytometry, and what can it do for you? The Basis: Conventional…

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The Exciting (and Emitting) World of Fluorescence

Flow cytometry is a fluorescence-based technology, as is fluorescence microscopy and confocal microscopy. Fluorescence is fundamental to how a cytometer gathers data, but I am often surprised, as a core manager, at how little new users know about the process of fluorescence. So, this is where I always start the training process. Let’s get physical…

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Sorting Large Cells and Materials by Flow Cytometry

Flow cytometers and cell sorters were designed with blood cells in mind. This means that commercial cell sorters are optimized for sorting cells typically smaller than about 20 µm in diameter. However, it turns out that many cell types, including those of mammals, are larger than 20 µm. So what are your options if you…

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Catching Greatness: Measuring Cellular Degranulation

One of the key characteristics of cytotoxic cells (i.e. CD8+ T cells, natural killer cells) is the presence of pre-formed cytoplasmic lysosomal granules. These structures house perforin and granzyme; two molecules that are essential for the lysis of target cells. Upon effector cell activation, granules are polarized toward the target cell and the contents are…

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An Introduction to Spectral Overlap and Compensation Protocols in Flow Cytometry

It strikes fear into the hearts of new cytometrists. Compensation. More fights have started over the proper way to compensate at meetings than anything else. This article will strive to shed some light on the principles of compensation, and equip you with the tools necessary to achieve compensation mastery for your research experiments. Compensation is…

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What Is A Biomarker? Definitions, Types, And Research Applications Explained

During the past decade or two, the field of biomarkers (short for biological markers) has witnessed immense development. The complexity of the field mirrors its multi-faceted applications, and it is easy to get confused with the different terms used in different contexts. Hopefully, this article will help make things clearer by explaining “what is a…

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5 Ways to Improve Your Fluorescent Protein Sorting

If, like many people, you use fluorescent proteins to view your transfection efficiency or your CRISPR gene editing, you can also isolate cells with different expression levels of fluorescent proteins. Here are 5 ways to improve your sorting experiment.

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