CHO cells can be stored for long-term storage at very low temperatures using cryopreservation. Here is a general protocol for CHO cell storage:
- Grow CHO cells to a density of 70-80% confluence in a culture flask or dish.
- Remove the old culture media from the flask and add pre-warmed trypsin-EDTA solution to cover the surface of the cells.
- Incubate the flask at 37°C for 3-5 minutes, or until the cells have detached from the surface.
- Add enough pre-warmed culture media to neutralize the trypsin-EDTA solution and transfer the cell suspension to a sterile centrifuge tube.
- Centrifuge the cell suspension at 150 x g for 5 minutes.
- Aspirate the supernatant and resuspend the cell pellet in a freezing medium containing 10% DMSO (dimethyl sulfoxide) and 90% fetal bovine serum (FBS) or other serum-free media.
- Transfer the cell suspension to cryovials or freezing bags, and place them in a controlled-rate freezer or in a -80°C freezer for at least 24 hours.
- Transfer the cryovials or freezing bags to liquid nitrogen storage for long-term storage.
When needed, cells can be thawed from the cryopreserved state by rapidly warming the cells to 37°C and culturing in fresh media. It is important to note that cells should be thawed quickly and handled carefully during the thawing process to ensure optimal cell viability and recovery.