R&D Services

Traditional mammalian cell culture is usually anchor-dependent and serum-supplemented, which directly results in a series of disadvantages due to the variability caused by serum/animal-derived components. In contrast, suspension cultures in animal-derived component free (ADCF) cell culture media have several advantages:

• reduced lot-to-lot variability of the medium
• easier scale-up
• no risk of blood-borne pathogens
• massively reduced production costs
• increased animal welfare

Because of these advantages, suspension cultures in animal-derived component free (ADCF) cell culture media are usually preferred for situations like recombinant protein production or viral vector and virus production due to their suitability for industrial processing and scale-up. However, transitioning from an adherent to suspension serum-free culture has its own set of challenges and is time consuming.

Xell’s scientists have more than 20 years of experience with cell culture and state-of-the-art culture media. Adapting cell lines to serum-free suspension cultures is just one of the many services we offer to the scientific community and biotechnology industry. We adapt your adherently growing cell line (suspension) for growth in a suitable serum-free, chemically defined cell culture medium of your choice. For more insight, feel free to read our technical note on this topic.

FIGURE: Infographic depicting general steps in the cell line adaptation process.

With our broad range of analytical methods (cell growth, product quantification and qualification, flow cytometry applications, qPCR/ddPCR), we offer detailed characterization of your cell lines. Cell line stability and selection pressure are potential issues to be addressed. Depending on the culture medium, the concentration of selection reagents may need to be adapted to guarantee stable production while maintaining high process performance. Furthermore, we recommend the evaluation of long-term stability which can be critical when extended seed-train periods are necessary.

FIGURE 1: Comparison of process values for a monoclonal antibody (mAb)-producing CHO cell line at three time points over a high passage experiment. Peak viable cell density was measured in bioreactor batch cultivations. mAb titer was determined by HPLC and relative gene levels were measured by quantitative real-time PCR. Loss of productivity was detected in long-term culture and was attributed to product gene loss.

FIGURE 2: Flow cytometric analysis of a CHO cell line cultivated in a high passage experiment. Heavy and light antibody chains were measured after intracellular staining with fluorescently labeled antibodies. A subpopulation with no HC expression was already detected in the mid-term culture. The long-term culture exhibited no HC expression and reduced LC expression. These results are reflected by the HPLC measurements of mAb titers (see FIGURE 1).

With our key competences in medium development and manufacture, we know that raw materials (production, origin, quality) and production technology are crucial factors in influencing the quality of the final medium product. As a result, the same medium formulation can lead to deviating process performances (see FIGURES 2 and 3). We therefore offer to analyze and test raw material sources and to compare different suppliers. Furthermore, we recommend the respective biological testing of potential raw materials and the evaluation of products from different suppliers with regard to process performance and production. Powder and liquid media characterization as well as solubility studies of your products are also part of our portfolio.

For a more detailed example of our raw material analysis skills, read our technical note on trace element impurities in amino acids of different suppliers .

FIGURE 1: Impurities found in tyrosine samples from different suppliers. The greatest impurities occurred with: Iron (Fe), Molybdenum (Mo) and Chromium (Cr).

FIGURE 2: Comparison of the growth performance of a HEK cell line in pre-culture passaging and batch cultivation with one medium formulation containing different variants (1-5) of one raw material for each culture.

FIGURE 3: Peak viable cell densities achieved in batch shaker cultivations with the same medium formulation produced by two different suppliers for three CHO cell lines.

Lot-to-lot variation is a well-known effect in media production and can occur even in chemically defined media. It can be caused, for example, through a change of raw materials or as a result of minor changes in the powder production process or the solubilization procedure. Furthermore, lot-to-lot variation can occur due to impurities in raw materials. Components such as amino acids in USP/pharma grade with ≥ 98-99% purity may still contain foreign amino acids and trace metals (see our technical note on trace element impurities). To evaluate variation in your media lots, we highly recommend biological performance tests and respective analytics. For this, we can establish and perform routine lot testing (see FIGURE).

FIGURE: In-house testing of different medium lots of a chemically defined medium formulation developed by Xell. The test was performed with a CHO cell line to define thresholds for biological performance testing of the powder lots.

Process development, such as feed strategy optimization, can take up a lot of time and resources. With our long-standing experience in cell culture technologies and medium development, we can provide process development services including:

• Development/optimization of a feeding strategy
• Metabolic optimization of feeding
• Optimization of seed trains and handling procedures
• Parameter profiles, e.g., pH, temperature and DO
• Development/optimization of perfusion processes

View our exemplary project.

FIGURE: Optimization of a perfusion process from initial to final process.

Cell culture medium is a liquid designed to support the growth of cells in an artificial environment. Usually, it contains a mixture of:

• an energy source like carbohydrates in the form of sugars
• amino acids since they are the building blocks of proteins
• fatty acids and lipids – particularly important in serum-free media
• inorganic salts to maintain osmotic balance
• vitamins and trace elements essential for the growth and proliferation of cells
• buffering system to maintain the pH in the physiological range

Cell culture feed is a liquid supplement that is mainly used in fed-batch cell culture processes and supports superior production by increasing the final cell density and extending the production capability of the cultures compared to batch process. It contains highly concentrated nutrients to increase the productivity of cultured cells. Consumed substances like vitamins and amino acids are replenished to extend the process and thereby increase product yield.

Selecting the best matching medium and feed for your cells is highly essential as it is the easiest way to generate maximum product yields. However, choosing the best medium can be quite a challenge and requires a lot of knowledge, not only about the cell’s requirements but also about the available options.

The selection process typically involves screening and benchmarking alternative off-the-shelf culture media from several suppliers. With our long-standing experience in cell culture technologies and medium development, we can provide expertise and resources for these routine studies. We will include any chemically defined media of your choice, not limited to media produced by Xell.

If you are just beginning to set up a cell culture lab or you are experiencing process limitations, problems in your scale-up or perhaps seeing batch-to-batch variations in your current medium, we are your trusted partner for scientific consulting. With years of experience in cell culture technologies, medium development and medium production in liquid and powder form, we deliver rapid and targeted support for your challenges. For example, we can work with your in-house spent media data to help optimize a process or feeding strategy. Consulting can also include on-site support if required.