Spin ~3X107 cells @ 500xg for 5min.
Save 1.5 ml conditioned media
Mix w/ 1.5 ml fresh media
Add 225 ml DMSO (7.5%)
Sterile filter 3.0 ml media
Resuspend cells in sterile freezing media
Aliquot 1.5 ml in 2 ml cryovials
Freeze in -80°C freezer overnight (in foam box to slow cooling)
Store long-term in liquid N2