What is cell passaging and why is it so important?
Behind every great discovery in biotechnology lies hundreds of thousands of hours of grinding work from bench scientists around the world. We take it for granted that their work is important and delicate but one thing you might not have asked yourself is what are they actually doing all day?
While you might imagine that these highly skilled scientists at the top of their fields are constantly working on cutting edge new experiments, the truth can actually be a lot less glamorous. A huge amount of time in biotechnology labs is spent on the tedious, routine work of cell culture maintenance (i.e. keeping cells happy and healthy ready for experiments). A typical bench scientist can spend around a month of their year caring for just one of their cell lines and yet this process is still highly manual.
One of the most common and fundamental processes to maintain cells is cell passaging. This process involves transferring cells from an overcrowded container to a new one with fresh growth medium to ensure their continued growth. This technique ensures that cells have sufficient nutrients, space and a suitable environment that allows them to remain healthy and grow.
Why is cell passaging important?
Cells are one of the most critical components of biological experiments, used for testing drugs preclinically, studying diseases, and even testing the safety of cosmetics and chemicals. Without cell passaging none of this would be possible. It is critical for many reasons:
Maintaining Cell Health: Over time, cells in culture consume nutrients and produce waste. Passaging helps maintain an optimal environment by providing fresh nutrients and removing waste products.
Preventing Overcrowding: As cells proliferate, they can become overcrowded, leading to competition for resources. Passaging ensures that cells have enough space to grow and divide.
Longevity of Cell Lines: Continuous passaging allows cell lines to be maintained over extended periods, which is essential for long-term studies and applications.
Optimal Growth Conditions: Different cell types have specific requirements for growth medium, temperature, and CO2 levels. Passaging helps maintain these optimal conditions, ensuring the cells thrive.
Consistency in Experiments: Regular passaging ensures that cells remain in a consistent state, which is crucial for reproducibility in experiments and product development.
Consistency of experiments is a key problem in this industry. Over 70% of scientists in the biomedical field have tried and failed to reproduce someone else's results . The lack of reproducibility in this field is estimated to cost $28Bn per year in pre-clinical research in the United States alone.
Given how time-consuming this process is, and the importance of consistency in experiments, one would expect it to be a prime candidate for automation. Despite this the vast majority of cell passaging is performed manually. To understand why we need to examine the process.
The process of cell passaging
Cell passaging in action
The process of cell passaging may differ depending on cell type but this article will focus on adherent cell passaging – that is cells which grow stuck to their plastic containers. There are many different types of adherent cells from neurons through to stem cells.
Cell passaging can be broken down into several key steps:
Material Preparation: Before starting, all necessary materials including culture flasks, growth medium, trypsin (for adherent cells), culture hood and the hands of our hard working scientist are prepared and sterilized.
Detachment: For adherent cells, a detachment solution (e.g. Trypsin) is used to help detach cells from the surface. First, the old media in the culture vessel is removed and the remaining cells are washed with a saline solution. The detachment solution is then added to the cells and the whole container is moved to the incubator for a set time. Once our scientist has waited about for 10+ minutes they move the container back to the culture hood. If the cell are not yet fully detached then mechanical agitation may be used here. Methods for this vary massively from scientist to scientist and lab to lab. Now we neutralise the detachment solution by adding fresh media.
Centrifugation: Now we want to change the media so the contents of the culture vessel are placed in a tube which goes into a centrifuge. Once the centrifuge has been balanced we’re ready to spin the cells down for 5-10 minutes until they form a dense pellet. We can then transfer them back to the culture hood and pipette out the liquid.
Resuspension or Dilution : The detached cells are then resuspended in fresh growth medium. The dilution ratio depends on the cell type and the desired cell density.
Seeding: The diluted cell suspension is pipetted into new culture vessels, where the cells will continue to grow and proliferate in the incubator.
How does Impulsonics help?
As you can see, cell passaging is quite an involved process requiring multiple bulky interconnected machines and manual steps. To automate requires at least five machines to work reliably and harmoniously together making it extremely difficult to reliably automate – which is why most people don’t bother.
At Impulsonics, our unique acoustic wave technology allows us to move, detach and collect cells without touching them inside their existing containers, facilitating an end-to-end adherent cell passaging in highly scalable benchtop device. We hope this technology will enable a new generation of medicines through higher quality and larger volumes of data.
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