Can a phosphorothioated oligo for antisense studies be used in medium containing serum, and what will be its half-life?

Antisense oligos containing phosphorothioate bonds can be used in medium containing serum. However, it is recommended that you inactivate the exonucleases in the serum to decrease the chances of degradation even when protecting modifications (such as phosphorothioate bonds) are present. Exonuclease inactivation can be accomplished by heating at 65°C (instead of 56°C) for 30 minutes.The half life of such an antisense oligo will be dependent on the target transcript, the cell type, and the antisense construct, resulting in no set average for this number.

Examples of oligonucleotide stability studies in serum can be found in the following references:

1. Lennox KA, Behlke MA. A direct comparison of anti-microRNA oligonucleotide potency. Pharm Res. 2010;27(9):1788-1799.
2. Lennox KA, Owczarzy R, Thomas DM, Walder JA, Behlke MA. Improved Performance of Anti-miRNA Oligonucleotides Using a Novel Non-Nucleotide Modifier. Mol Ther Nucleic Acids. 2013;2(8):e117. Published 2013 Aug 27.