Saliva is reflective of an individual’s health or disease state. Additionally, it requires minimal equipment to collect, collection is non-invasive and storage is comparably inexpensive. Further, because saliva is not sterile, it is not susceptible to the same risks of microbial contamination, which influences sample quality. Nonetheless, collection method, time and volume are all important considerations for the collection process. Therefore, Rosa et al. (2016) have established standard operating procedures for saliva characterization for storage.1
The authors collected 22 saliva samples from healthy volunteers. They asked the volunteers to refrain from eating, drinking or performing oral hygiene procedures for one hour before saliva collection. Immediately prior to collection, the volunteers rinsed their mouths with clean water for 30 seconds to remove desquamated epithelial cells, microorganisms, and food and drink remnants. After one minute, the authors used one of three collection methods:
- Passive drooling: The authors used a 50 ml sterile tube to collect passive saliva over three minutes.
- Sublingual cotton roll: They placed a cotton roll under the tongue for two minutes and then put the rolls in a 15 m sterile plastic tube with a sterile 100 ml pipette tip in the bottom to facilitate saliva collection by centrifugation at 10,000 g for 10 minutes at 4ºC.
- Vestibular cotton roll: The researchers followed the same procedure as for the sublingual roll, but placed the cotton roll in the vestibular area of the mouth.
The researchers also assessed intra-individual variability by collecting further samples from eight healthy donors at 11 different times for five months.
In terms of volume, Rosa et al. found that the collection method that produced the greatest volume protein concentration was the sublingual method. They also found that time of day affected the amount of saliva collected, with there being less in the afternoon. Gel electrophoresis demonstrated that there are proteins that are different between individuals even though all the individuals are considered healthy. They identified a total of 19 protein groups with molecular weights varying between 9.2 kDa and 157.6 kDa. They identified 5 of these that were present in all individuals. Using capillary electrophoresis, they found protein degradation at room temperature was not significant within the first 24 hours after collection.
Rosa et al. have demonstrated that it is possible to obtain saliva samples suitable for biobank storage using an easy and inexpensive method.
Rosa, N., et al. (2016) “Protein quality assessment on saliva samples for biobanking purposes,” Biopreservation and Biobanking [Epub ahead of print].