Solving the challenges of standardizing cell counting to ensure reproducibility in experiments, assays and manufacturing processes



In this podcast we talked with Christian Berg, Global Product Manager at Chemometec about the importance of standardizing cell counting because while often overlooked, it is essential for reproducibility in experiments, assays and manufacturing processes. Cell counting is a challenging technique, with many pitfalls, that can delay entire projects. We discussed how new technologies are solving these challenges and enabling standardization of cell counting across organizations.

Show Notes

I began our interview by asking Mr. Berg if he could tell listeners why cell counting is so important. He explained that there are some applications where it is clear why cell counting is important, for example when cells are used for manufacturing pharmaceuticals. In biomanufacturing, you need cell counting to perform bioassays for toxicology testing, for use in quality testing of products and to measure the activity of the final product by using cells to report the activity of the drug. Most importantly these cell counting methods must be standardized.

He went on to say that with the emergence of cell therapies, you have completely new processes and new requirements for cell counting and companies must rethink how they count cells and what quality parameters they should focus on.

When you look at cell counting in the context of research, it is used as a tool to maintain the cells in culture while setting up experiments. However, the need for standardization is critical as cell density is very important for how cells function. Cell density influences powerful signaling pathways that can impact any biological function under study, so standardizing the cell counting in a lab is key to achieving reproducibility of a specific assay. Another challenge in cell counting is data management. For instance with cell therapies one must scale the process tremendously, so you might have hundreds of cell counting units, thus it will be important that the incoming data is easy to organize.

Next, I asked Christian if he could talk about how cell counting needs have evolved with new research and manufacturing demands. He said that in research the trend is towards larger experiments, such as cell based screening assays. With large experimental setups, it is very important that the system is optimized with a consistent counting method to reduce day-to-day variation of the experimental setup. He also discussed the reproducibility crisis in research where several of the published articles in peer review journals cannot be reproduced by other researchers. There have been many suggestions about how to correct this problem and standardization is one of them.

He said that at Chemometec, they are seeing a lot of interest from research leaders looking to standardize the laboratory methods. When Chemometec goes to labs that are using manual counting. The team typically asks a handful of researchers to perform manual counting on the same sample. It is not uncommon to see a forty percent variation between the researchers. This makes a big impact as that kind of variation is a big problem for a research group, but it also makes collaboration with other partners more difficult.

Then we discussed the challenges of cell counting. Christian described how the most significant challenges in cell counting today can be split into two groups – technical challenges with performance of the cell counting and practical challenges when cell counting is used in a specific operation or research.

With bioprocessing, customers typically use older generations of cell counters that are mechanically complex and contain tubing, which is inherently unstable and causes instruments to break down quite often. If a cell counter breaks down, it is time consuming and expensive to fix. This is a technical challenge.

Conversely, he said that data management is a practical challenge that can be clearly seen in virus and cell therapy manufacturing. For these types of manufacturing, you cannot build a bigger steel tank if you want to increase production. Instead, you are forced to scale out the production setup, which means that you need more analytical equipment to support the production. He shared that Chemometec has customers that have hundreds of cell counters to support manufacturing needs and having good reliable data integration is essential to be able to control these processes. Therefore it is important to consider the performance of the cell counter as well as the implementation of the cell counting method in your process.

I then asked Christian to talk about Chemometec’s recently launched next generation version of their popular NucleoCounter NC-200, the NuceloCounter NC-202. He explained that the NC-200 is actually a third generation counter and it represents a general overhaul of the hardware, the cassette and the software. They have updated the optics electronics as well as the cassette, and the camera. They have also improved the light sources, which improve the quality of the images. This quality improvement permits a greater extraction of detail about the sample and led to improvements of the performance of the instrument. For example, they increased the dynamic range to ten million cells and at the same time reduced the time it takes to conduct a cell count to thirty seconds. The improved data quality also permits viewing of much smaller particles and the ability to quantify cellular debris for increased robustness.

He went on to state that cell therapy has very high requirements for the scalability of analytical instrumentation. Chemometec developed NC-202 to meet these demands by using modern tools to centralize data. We expect a large increase in the use of robotics and automation efforts will probably revolve around MES systems that will allow operators to integrate the different analytical and manufacturing instrumentation on a single platform to allow more effective control of the manufacturing processes.

I followed up by asking about specific industry segments, and the ways in which cell counting can improve these processes. We started with biologics manufacturing. Christian explained that in biologics manufacturing the cell lines are used to produce therapeutic proteins, so cell counting is employed to control these processes. There are different modes in which the cells can be grown, but in all cases the cell counting is a very important analytical parameter for decision making. The cell lines that are used in biologics manufacturing are not the hardest cell lines to count, but the stability of the automated cell counting unit can be a challenge. The challenge lies in the instability of many of the older generations of cell counters that are mechanically complex and contain internal fluidics that can clog the system. When a cell counting instrument breaks down during a process that can be very unfortunate, because quite often instruments measure differently. This can cause a systematic difference in the cell count, which will affect the data that you are monitoring. It can also affect the evaluation of the quality of the final product. One important feature of the NC-202 to is that all the units will measure the same regardless of production year. Chemometec achieves this by using a very rigorous calibration during manufacturing.

Then I asked if he could talk about cell therapy and virus manufacturing processes. He explained that in comparison to biologics manufacturing, the production of virus and cell therapies are much more difficult to scale. In virus manufacturing, the cell lines that are used to expand the virus are quite diverse because specific viruses have preferences for specific cell types. As a result, there is no single cell line available that can be used for the expansion of all viruses. In addition, most of the cell lines used are adherent, which are much more difficult to scale compared to suspension cells like CHO cells. In order to overcome the scalability problem with adherent systems, companies use microcarriers, which allow the cells to be grown in bioreactors. However, counting cells on microcarriers is not trivial because you cannot count the cells while they sit on the microcarriers. You need to strip the cells off the microcarriers prior to counting and that process together with the actual counting can take up to thirty minutes.

He described a recent case where a large virus manufacturer came to Chemometec and asked for help with setting up a cell counting method for counting primary cells. They used manual cell counting where operators would put the cells into five categories manually. This counting process was very extensive and took more than 30 minutes for a single cell count. Using the NC202, Chemometec provided the manufacturer with an assay that allowed them to automatically perform cell counting, thus reducing the analysis time from thirty minutes to thirty seconds.

Next I asked Christian to describe what the implementation of the NucleoCounter looks like for scientists interested in incorporating this into their workflow. He explained that the NucleoCounter is very easy to use and that is particularly important if you want to standardize a process. The cassette in the NucleoCounter replaces three workflow steps still present in other counting methods – the addition of dye, the loading of the cells into a counting chamber and the focusing required before performing the cell count.

He summarized by saying that the simplicity of the NucleoCounter operation will make it much easier to implement in any process, because the standard operation procedures are shorter and it is easier to train new people to use the instrument. Another important advantage of the NC-202 is that it can easily be deployed in clean rooms. It is easy to clean and it doesn’t require any maintenance, regular validation is enough to ensure consistent performance of the instrument.

I closed the interview by asking Christian if he had anything that he would like to add for listeners. He said Chemometec is still operational, so if companies would like to try the NucleoCounter, please contact them. Normally they would send out field application scientists to get companies started, but because of these unusual times they made a video to demonstrate setting up the instrument and getting started. Typically a week is sufficient to test the performance of the NucleoCounter with other cell counting systems.

For more information about the NucleoCounter, please see


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