The shelf life of an oligonucleotide is determined by three factors.
1. Sensitivity to pH
In contrast to double strand DNA, single strand oligonucleotides have a significantly higher sensitivity to acidic pH values. Therefore, it is recommended that the media used for resuspension of the oligonucleotides lies in the basic pH range.
2. Nuclease degradation
There is a danger of degradation of the oligonucleotides through nuclease activity. This nuclease degradation is hastened by the presence of salts, in particular by two-valent and three-valent ions. Avoiding the introduction of such nucleases by taking suitable hygiene measures at the workplace, and the addition of low amounts of ethylenediamine tetra-acetic acid (EDTA) can be helpful.
3. Freeze/thaw sensitivity
Single stranded oligos can be affected by freezing and thawing cycles. Keeping these cycles to a minimum will ensure oligo integrity. Dispensing the master stock of oligo upon receipt into usable aliquots is good practice to reduce repeated handling.