Probably will want to add some glycerol too and purge the tube atmosphere with argon/nitrogen to reduce oxidation (freezer burn).

The faster you freeze them the smaller the ice crystals, so the less damage they will sustain, meaning flash freezing in liquid N2 is probably best.

Hi Sam Siljee

For preserving lentiviral activity, store your lentiviruses in small aliquots to avoid freeze-thaw cycles. Adding cryoprotectants like 0.5M sucrose and 0.6mg/ml BSA, as suggested by Bandeira et al., can help maintain viral integrity during freezing. When freezing, flash-freezing in liquid nitrogen is generally more effective than ethanol/dry ice for preserving viral titer, as it ensures rapid transition to the frozen state, minimizing potential damage to the viral particles. Once flash-frozen, store the aliquots at -80°C.

Thank you Robert Adolf Brinzer and Saman Behboodi Tanourlouee for your suggestions!

Sam