Frequently Asked Questions

FAQ

Cell Cultivation and the Cellab® Bioreactor System

Hollow Fiber System

Scaffold Holder

Control Center

  

Cell Cultivation and the Cellab® Bioreactor System

Why should I use hollow fiber technology for my cell cultivation instead of the traditional bioreactors?
T-Flasks, roller bottles and stirred tank bioreactors are all 1-compartment systems where the supply of nutrients, the removal of metabolites (e.g. ammonium and lactate) and cell harvesting requires a complete medium exchange.

On the other hand, the Cellab® Bioreactor System is a 2-compartment system whose semipermeable membrane separates the cells from the media and therefore provides a more in-vivo like culture environment. The membrane allows for free mass transfer via diffusion between the cell and medium compartments. The defined cut-off retains cells, proteins and high molecular weight growth supplements in the cell compartment. The result is a highly concentrated cell culture product with less need for growth factor supplementation. In addition, it also reduces the risk of contamination and the amount of consumables and media required.

All in all, the total supernatant volume using the Cellab® Bioreactor System is about 10 to 50 times less (depending on the cell line) compared to 1-compartment culture systems. For example: Using a T300-Flask, the harvest volume would be 150 ml and the corresponding volume out of a Cellab hollow fiber bioreactor will be only 3-15 ml for an equivalent amount of cells.

Cellab Bioreactor System

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What type of cells can be cultured in the Cellab® Bioreactor System?
Hollow fiber bioreactors can be used for both suspension and adherent cell lines. Suspension cells are typically cultured in the extra capillary space (ECS) and adherent cells in the intra capillary space (ICS). Standard cell lines for cultivation in the ECS are hybridoma for monoclonal antibody (mAb) production or CHO (Chinese hamster ovary) for production of mAbs and other recombinant proteins. Also Mesenchymal Stem Cells (MSC) / induced Pluripotent stem cells (iPSC) can be cultured in a hollow fiber system (typically cultivated in the ICS) as well as many other cell lines. Additionally, it is also possible to culture animal, insect cells and plant cells.

Example of cell lines that can be cultured with the Cellab® bioreactor system
- Hybridoma cell lines
- CHO (Chinese Hamster Ovary)
- HEK (Human Embryonic Kidney)
- MSC (Mesenchymal stem cells)
- Keratinocytes
- Epithelial cells

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How do I determine if my protein producing cell line could work in the hollow fiber system?
The most important factor is to have a suitable MWCO (Molecular Weight Cut-Off) to achieve a sufficient separation. The MWCO of the membrane is said to be the molecular weight of the smallest solute which is at least 90% retained (the smallest solute for which the permeation is 10% or less).
A rule of thumb is to choose a minimal MWCO by selecting an MWCO value about half of the molecular weight of the larger molecules to be retained in order to achieve a minimum 90% retention (best practice being a ratio of 1:5).

Example:
You desire to retain a protein produced by your cell line with 100 kDa. The suitable MWCO is between 10-20 kDa.

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How many antibodies can I produce with the largest available Cellab® Hollow Fiber Bioreactor System?
With a hollow fiber L system one can achieve up to 170 mg of antibody depending on the individual production rate from the cell line.

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What is the average time for purification? How much time can be saved?
Given the 10x to 50x increase in cultured cell densities, the purification time is greatly reduced. The use of chromatography columns with protein G, Protein A etc. requires dilution of the original volume 1:1 with a binding buffer. In the case of a 10x volume reduction with the Cellab® Bioreactor System, 100 ml of pre concentrated supernatant is generated which must be diluted with 100 ml of binding buffer. In case of single compartment systems, there are 1,000 ml of supernatant which has to be diluted with 1,000 ml of binding buffer with a final volume of 2,000 ml. If there is a volume reduction of 50x with the Cellab® Bioreactor System, there is only 20 ml supernatant and 40 ml total volume for the purification. Therefore the time saving is at least 90%.

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How can antibody quality be improved?
High quality cells are essential for an optimal production of antibodies. This requires that all necessary biochemical components be available to produce those antibodies. If certain biochemical components are missing in the media, the antibodies could be incomplete or fragmented. This could also result in the function of the antibody being disturbed which can lead to a waste of resources spent on ineffective antibodies. Using the Cellab® Bioreactor System ensures a sufficient supply of necessary biochemical components due to the continuous circulation and exchange of cell culture medium which achieves reliability, reproducibility and precision in your cell culture.

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How do I harvest adherent cell lines from the Cellab® Bioreactor System?
For culturing adherent cell lines we recommend cultivation of these cells in the ICS (intra capillar space) of the hollow fiber. For harvest, the adherent cells must be treated with a cell detachment soltution like Trypsin or Accutase® (Accutase is a registered trademark of Innovative Cell Technologies, Inc.) . The harvest can then be performed using two syringes at the ICS ports. In this process, the user pushes on an empty syringe to flush the cell suspension from the ICS of the bioreactor into the second syringe at the other side. The entire cell suspension can be collected in one of the syringes.

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Why is a "gas transfer module" included in the Cellab® Bioreactor System?
The gas transfer module is designed for the aeration and/or degassing of liquids. The gas transfer module is equipped with a gas selective membrane where gas molecules like oxygen or CO2 can pass through and larger molecules as well as liquids are retained. The working principle is that oxygen-rich air from the environment (incubator atmosphere) is pumped via the gas pump into the fiber surrounding area of the gas transfer module. Only gases diffuse through the membrane into the cell culture medium inside of the fibers. Therefore, the fibers within the gas transfer module serve as a sterile barrier. Oxygen-enriched medium then flows to the bioreactor and directly to the cells.
Additionally, an external gas supply can be connected to the docking station to provide individual gas mixtures or concentrations inside the system (e.g. nitrogen).

Cellab gas transfer module

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What type of gas supply can I connect to the docking station?
For standard applications no external gas supply is required.

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Can we culture different types of cells at the same time?
It is possible to culture up to 5 different cell types using the disposable set with 5 small hollow fiber modules or the disposable set with 5 scaffold holders.

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Can I use the Cellab® Bioreactor System for upscaling?
Cellab offers a range of hollow fiber modules from about 100 cm² up to 2500 cm² of culture surface area. This allows the progression to larger modules without the need to validate a new system. Single hollow fiber modules with an even higher surface up to 25.000cm2 are available on request.

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How long can I culture cells using the Cellab® Bioreactor System?
Depending on the cell line and your laboratory praxis, cells can be sustained in hollow fiber bioreactors for several months while a continuous harvest of protein is possible. Neither a replacement of the bioreactor itself no cell passaging is necessary during the culture period in Cellab bioreactors.

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Hollow Fiber System

How is it possible to detect the right time for cell harvesting in hollow fiber modules?
One option is to measure the concentration of metabolites released during the proliferation process and compare it with a reference curve from a culture process in a T-Flask. Our recommendation is to use the first process run for evaluation purposes to detect all relevant information and establish the process.

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Scaffold Holder

How does the harvest process work for MSC from a scaffold?
In most applications where stem cells are cultivated in a scaffold, the cell products will not be harvested from the scaffold. After the stem cells differentiate into specific cell types in combination with a particular scaffold, the scaffold and the supernatant are typically analyzed together without extracting the cells from the scaffold. For applications in the field of human implant development , the regulatory aspects for a medical device will apply.

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Control Center

How does the docking station operate? Must the docking station be connected to the computer at all times?
The Cellab® Docking Station is a reusable device which controls and monitors the disposable set in conjunction with the control computer. The docking station is easy to use and requires only a few manipulations for its proper functioning. Once the media bag is filled, you only need to connect the media and the gas pumps using the tubes provided. After installation, the docking station communicates via a USB-connection cable with any Windows computer and can remain in the incubator.. After starting a cell culture program in the automatic mode of the docking station the control computer can be disconnected. Feel free to contact us if you have any question concerning the operation of the Cellab® Bioreactor System.

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What types of incubators are compatible with docking station?
The docking station is suitable for nearly every standard CO2 incubator. The only requirement is that the incubator needs an adequate access port either at the back or the front to insert the cables (Power and USB) through.

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