Why new standards in cell counting are needed for accurate results

Cell counting is a fundamental procedure in both research and biomanufacturing, including cell therapy. Though it should be a straightforward and reliable process, it can be known as an error-prone, time-consuming and highly subjective technique.

In this free SelectScience^® webinar, now available on demand, Karine Labour, EU Managing Director at Logos Biosystems, describes the benefits of its latest automated cell counter, the LUNA-FX7TM. Labour explains how this instrument enables users to standardize cell counting in the lab, with different options available for counting methods, dyes, and the key parameters to consider.

Register now to watch the webinar on demand, and read on for highlights from the Q&A discussion.

How often do you need to calibrate the instrument?

KL: It depends on which instrument we're talking about, and you need to follow the recommendations from the manufacturers. When it comes to the LUNA-FX7™ or any LUNA counters, there are a few times when we recommend you calibrate the instrument. After software updates, it's recommended to do a calibration, or following a service, or after any modification to the instrument. Also, if you're filling in compliance or if you do regular IQ/OQ. Otherwise, there is no real need for routine maintenance with the instruments, though calibrating once a year is a good idea.

When do you recommend using erythrosine dye?

KL: Erythrosine B is a safe dye so it's useful in brightfield to replace trypan blue as this is toxic; it's carcinogenic, teratogen, mutagenic, etc. So, erythrosine B can be used as a direct replacement to trypan blue whenever your instrument is compatible.

The LUNA-FX7™ is compatible, and all the LUNA counters are compatible with erythrosine B. So, feel free to use this safe dye as soon as you can. Taking away any toxic compound from your lab is always a good idea.

Can the LUNA family of devices count yeasts?

KL: Absolutely, yeast can be counted with the LUNA-FX7™. You don't need a brightfield, you can use total counts of your yeast cells. Even if you have clusters or budding cells you can count them. As soon as you are interested in viability, you need to use fluorescence. Acridine orange, or propidium iodide can work in most cases, but sometimes there are counting difficulties, like Candida, for example. For that, we have other viability kits which are available and can be used with the FX7™ to count here. So yes, it's absolutely possible.

How can you count very small-size cells, for example, less than 7 μm, more accurately?

KL: Small cells require fluorescence, especially when you use an image-based cell counter. With image-based cell counters in brightfield, the cell count will be valid down to 8 μm, but if the cells are smaller, many questions arise.

In fluorescence, unlike brightfield, the size of the cells won't be a problem because it's going to be related to the fluorescence intensity of the cells when you use nucleic acid dyes like acridine orange and propidium iodide. Below 7 μm, or if you have different sizes of cells in your sample, switch to fluorescence and it would be absolutely accurate.

The only limit is the lower limit of the instrument. For example, if your cells are below 1 μm, you need a different technology. That's the case, for example, with bacteria. That's the only limit, but otherwise, fluorescence will accurately count cells.

Is there the possibility to count cells based on luminescence?

KL: As far as I know, there are kind of two types of luminescence. Flash luminescence, which is too fast to be seen on an instrument like a cell counter, and glow luminescence, which is going to be more stable, but less intense.

Whether it's going to fit with available light sources we have on the instrument would really depend on the fluorescence intensity and on the wavelength to be tested, depending on your samples. Usually, you're going to use microplate readers to check that.

To learn more about accurate and precise cell counting: Watch the webinar on demand >>

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