Can a phosphorothioated oligo be used in medium containing serum when using for antisense studies? How long is the half life in vitro?
Antisense oligos can be used in medium containing serum. However, you need to inactivate the exonucleases in the serum to decrease the chances of degredation (even though the oligos are protected by the phosphorothioate modification, there is always a chance, so better to err on the side of caution). You can do this by heat inactivatation at 65°C (instead of 56°C) for 30 minutes. As for a half life in vitro, that is totally dependent on the message, the cell type and the construct. There have been claims of 24 hours in vivo (mice), but again, there is no "set" or "average" half life.