Centrifuge cells at 300 – 400 × g for 4 – 5 minutes to obtain a cell pellet. Then aseptically remove the supernatant.
Suspend the pellet in cryopreservation solution at 2°C – 8°C. Mix thoroughly and transfer the suspension to a cryovial (e.g., 1.0 mL of suspension in a 1.5 mL cryovial).
Freeze the cells gradually (1°C – 2°C per minute) using a controlled rate freezing system and store the vials in liquid nitrogen (vapor phase). Alternately, place the vials in a freezing container and transfer to -80°C overnight. Transfer the cryovials into liquid nitrogen the following day – we recommend the vapor phase.
Determine the efficiency of cryopreservation by thawing one vial after 24 hours of storage in liquid nitrogen.