Adverse Effect of Air Exposure on the Stability of DNA Stored at Room Temperature

Biopreservation and Biobanking April 2011, Vol. 9, No.1

Marthe Colotte, Delphine Coudy, Sophie Tuffet, Jacques Bonnet

http://www.liebertonline.com/doi/abs/10.1089/bio.2010.0028

BACKGROUND: In view of the exponential increase of the number of DNA samples to be stored, classical conservation in freezers appears cumbersome, costly and subjected to the risks of natural disasters. Room temperature storage of dehydrated DNA appears as an alternative solution since:
• the main degradation pathways (depurination, base deamination, and base or sugar oxidation) of DNA involve water,
• solid state is known to generally slow down chemical processes because of reduction of molecular mobility and
• there are multiple examples of retrieval of DNA aged at room temperature.
However, DNA, even thoroughly dried, if left exposed to air regains a fair amount of water and still undergoes strand breaking and oxidation. Moreover, the presence of the atmospheric pollutant, ozone, very reactive toward DNA, should not be neglected. Thus, it appears that long-term storage of DNA at room temperature may require an absolute protection from the atmosphere. However this protection cannot be provided by plastic containers since they are known to be permeable to moisture vapour.
RESULTS: We therefore developed a new procedure for room temperature storage of DNA whereby DNA samples are stored under an anoxic and anhydrous atmosphere in small glass vials fitted in stainless-steel, laser-sealed capsules. Under these conditions, at room temperature or 70 °C, no DNA degradation was detected after 8 month or 1 week storage, while samples kept in air, in closed plastic tubes, either naked or in the presence of matrixes, underwent clear (or strong) degradation and/or aggregation.
CONCLUSION: This study demonstrates the necessity of protecting DNA from air in order to preserve its integrity for room temperature storage.