Long-term stability of DNA from saliva samples storedin the Oragene® self-collection kit†
R.M. Iwasiow, A. Desbois, H.C. Birnboim
DNA Genotek, Ottawa, Ontario, Canada

Storage of specimens by refrigeration or freezing cansignificantly increase costs. The Oragene® kit eliminates
these costs by allowing saliva specimens to be stored foryears at room temperature without DNA degradation.
This document presents evidence that Oragene/saliva
samples stored at room temperature maintain highmolecular weight DNA for at least 5 years.

Introduction
Large population-based studies, involving thousands ofsubjects, are increasingly being used to investigate thegenetic determinants of complex diseases. Saliva is aconvenient source of genomic DNA because it can becollected in a painless and non-invasive manner. For
logistical reasons, samples often need to be stored prior
to the extraction of DNA. Common storage methods,
such as refrigeration and freezing, can add significant
costs and inconvenience to a large genetic study.
Ideally, a kit that would allow saliva samples to be
stored at room temperature for long periods of timewith no significant degradation of the DNA would
be highly desirable. The Oragene kit is specificallydesigned for collecting and preserving DNA in saliva.
This technical bulletin provides evidence that theOragene kit can preserve the integrity of DNA insaliva at room temperature for many years, as wellas maintain stability at temperatures up to 50°C
for 187 days.

Materials and methods

DNA yield was determined by the highly specificFluorescence/DNase method2. The F/D method
quantifies DNA using SYBR Green I™ dye (MolecularProbes, Inc.), with or without DNase treatment.

ResultsSamples stored at 24°C, 37°C or 50°C
for up to 187 days
DNA from Oragene/saliva samples stored at 24°C and37°C had a molecular weight > 23,000 bp and showedno evidence of degradation at the indicated time
points (Figure 1). Samples stored at 50°C showed
only slight degradation at 187 days. There was nochange in the yield of DNA in any of the samples,regardless of storage temperature, as determinedby the F/D method.
24ºC
Days 061 187

37ºC
061 187

50ºC094 187

23.1 kb

Oragene/saliva samples were collected and stored ateither room temperature (24°C), 37°C or 50°C for
periods of time up to 187 days. In addition, saliva
samples from 7 donors collected in Oragene solution
and stored at room temperature for 5 years were†analyzed. Aliquots of the various samples were removed
and processed using the prepIT™•L2P (DNA Genotek)
purification protocol1. Approximately 200 ng ofDNA from each sample was analyzed by agarose
gel electrophoresis and ethidium bromide staining.
The size of the extracted DNA was determined bycomparison with a Lambda-Hind III digest ladder.

Figure 1: Agarose gel electrophoresis of DNA extracted
from Oragene/saliva samples. A Lambda-Hind III digest
was used as the marker in Lane 1.

Saliva samples were collected with Oragene®•DNA or Oragene®•DISCOVER.

(outside the USA)(in the USA)

Some DNA Genotek products may not be available in all geographic regions, contact your sales representative for details.

www.dnagenotek.com • support@dnagenotek.com

Samples stored at 24°C for 5 years
Saliva samples were collected in Oragene kits andstored undisturbed at room temperature for 5 years.
DNA was extracted and analyzed by agarose gelelectrophoresis. The results shown in Figure 2 indicatethat high molecular weight DNA can be extracted
from 5 year old samples that had been stored at 24°C.
ABCDEFGOragene/saliva samples stored at room temperature for
5 years were analyzed. In agreement with the prediction
from the accelerated-aging experiments, we havefound that the DNA was stable at room temperature;
the majority of the DNA remained > 23 kb in size
after 5 years (Figure 2).
In summary, Oragene/saliva samples in tightly closed
containers are expected to maintain the integrityof DNA at room temperature for at least 5 years.

Long-term storage recommendations

23.1 kb

Figure 2: Agarose gel electrophoresis of DNA extracted from Oragene/saliva samples stored at room temperature for 5 years.

The evidence presented here indicates that Oragene/saliva samples may be stored in tightly capped
containers at room temperature for many years withthe expectation that high molecular weight DNA
will still remain present. For longer-term storage,
it is recommended that unpurified Oragene/saliva
samples be distributed in aliquots and that thesealiquots be stored at -20°C or lower temperatures3.

Discussion and conclusions
Accelerated-aging studies of Oragene/saliva samples
stored at 50°C for 187 days indicated that DNA
would remain stable for at least 30 months at room
temperature (Figure 1). This was calculated using
the Arrhenius equation that is based upon theassumption that the rate of a chemical reaction
typically decreases by half for every 10°C decreasein temperature. Therefore the rate of chemicaldegradation of DNA at 24°C was expected to be
5-fold slower than the rate of degradation at 50°C.

References
123

Laboratory protocol for manual purification of DNA from 0.5 mL of sample. DNA Genotek. PD‑PR-006.
DNA quantification using the Fluorescence/DNase (F/D) assay. Replaced by DNA quantification using SYBR Green I dye and a
micro‑plate reader. DNA Genotek. PD-PR-075.
Long-term storage of Oragene®/saliva samples. DNA Genotek. PD-PR-012.

Oragene®•DNA is not available for sale in the United States.
Oragene®•DISCOVER is for research use only, not for use in diagnostic procedures.
®Oragene is a registered trademark and prepIT™ is a trademark of DNA Genotek Inc. All other brands and names contained herein are the property of their respective owners.
All DNA Genotek protocols, white papers and application notes, are available in the support section of our website at www.dnagenotek.com.

PD-WP-005 Issue 3/2011-11© 2011 DNA Genotek Inc., a subsidiary of OraSure Technologies, Inc., all rights reserved.

www.dnagenotek.com • support@dnagenotek.com

2