CD CHO Medium

Thermo Fisher Scientific offers multiple serum free media (SFM) and chemically defined (CD) media options for CHO cultures. For adherent cultures, CD CHO (10743-011) and CD OptiCHO medium (12681-011) are robust media; both are protein free and animal origin free (AOF). For adherent cultures, CD CHO-A (097-0182DJ) is a widely used protein free and animal origin free medium. There are other formulations available to suit other research needs; contact Technical Support for further information.

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Cells can be adapted by Sequential or Direct Adaptation. Suggested protocols for each are below, and you can also find more information by searching "Adaptation of Cell Cultures to a Serum-Free Medium" from our website home page.

SEQUENTIAL ADAPTATION
1) Subculture the cells growing in serum-supplemented medium into a 25%:75% mixture of SFM and serum supplemented medium.
2) When the cell density is 5 x 10E5 cells/ml, subculture the cells into a 50%:50% mixture of SFM and serum supplemented medium at a cell density 2.5 x 10E5 to 3 x 10E5 cells/ml.
3) Continue to subculture after the cell density 5 x 10E5 cells/ml in gradually increasing proportions of SFM until the serum is ~0.1% with about 85% cell viability.
4) Subculture the cells into SFM with an innoculum of 2.5 x 10E5 to 3 x 10E5 cells/ml.
5) When the cell density is 1 x 10E6 to 3 x 10E6 cells/ml (4 to 6 days post planting) subculture the cells again.
6) Stock cultures of SFM adapted cells should be subcultured in SFM every 3 to 5 days when the cell density is 1 x 10E6 to 3 x 10E6 cells/ml with 90% viability.

DIRECT ADAPTATION
Some cells can be directly adapted from serum-containing medium to SFM. For direct adaptation, the cell innoculum should be 1.5 x 10E5 to 3 x 10E5 cells/ml.
Cells should be subcultured when the cell density is 1 x 10E6 to 3 x 10E6 cells/ml. Cells are fully adapted to SFM when the cell density is 2 x 10E6 to 4 x 10E6 cells/ml after 4 to 7 days in culture.
Stock cultures of cells adapted to SFM should be subcultured in SFM every 3 to 5 days when the cell density is 1 x 10E6 to 3 x 10E6 cells/ml with 90% viability.

When cells meant to be grown in suspension are grown in static culture, they may form clumps. These clumps will severely limit transfection efficiency and protein expression. It is suggested that FreeStyle 293 cells in FreeStyle media and CHO-S cells in CD-CHO or CHO-SFM are grown in agitated suspension to reduce the appearance of clumps. However, if clumps do form, you can try the following protocol to select for cells that don't form clumps:

- Transfer cells into an appropriate size centrifuge tube that will hold the entire cell suspension.
- Allow cells to sit undisturbed for about 5 minutes. The time can vary depending on the specific cell line. Larger cell clumps will settle to the bottom of the tube.
- Collect cells from the upper portion of the tube to passage into a new flask.

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Some cells, such as insect cells, are sensitive to changes in their medium. By sequentially adapting cells, the medium is changed with minimal effects on cell growth.

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While the full formulation for 1X CD CHO Medium is proprietary information that cannot be disclosed, we can confirm that the medium contains a surfactant and that no additional surfactant would need to be added to the medium to support your suspension CHO cells in shake flask culture.

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