2012

Saliva Preservative for Diagnostic Purposes

This preservative can be used in remote areas without refrigeration for at least two months.

Saliva is an important body fluid for diagnostic purposes. Glycoproteins, glucose, steroids, DNA, and other molecules of diagnostic value are found in saliva. It is easier to collect as compared to blood or urine. Un for tunately, saliva also contains large numbers of bacteria that can release enzymes, which can degrade proteins and nucleic acids. These degradative enzymes destroy or reduce saliva’s diagnostic value. This innovation describes the formulation of a chemical preservative that prevents microbial growth and inactivates the degradative enzymes. This extends the time that saliva can be stored or transported without losing its diagnostic value. Multiple samples of saliva can be collected if needed without causing discomfort to the subject and it does not require any special facilities to handle after it is collected.

The preservative contains sodium dodecyl sulfate (SDS), ethylenediaminetetraacetic acid (EDTA), and Tris buffer. This preservative was developed to preserve saliva from astronauts during spaceflight without refrigeration to determine if virus DNA was present. Saliva with added preservative can be stored at room temperature for up to 60 days without any measureable degradation. Viral DNA is routinely measured from saliva stored in this manner without refrigeration. Thus, this preservative can be used to preserve critical macromolecules (nucleic acids and proteins) without consuming power resources. This preservative has been used on flight experiments aboard both the Space Shuttle and the International Space Station.

Saliva contains hormones such as cortisol and DHEA, cytokines (immune markers), DNA and RNA viruses, antibodies, and many other substances of diagnostic value. Saliva also contains many bacteria that produce proteases that destroy proteins, nucleases that destroy DNA and RNA, and other degradative enzymes. Typically, saliva and other body fluids are refrigerated (or frozen) to prevent or slow the degradation process. Refrigeration and freezers are extremely limited resources in spacecraft, undeveloped countries, and during activities away from electricity. Although not tested, the preservative is expected to be effective for other body fluids such as urine and blood. In addition, the toxicity of the preservative is very low.

The preservative consists of 0.5% sodium dodecysulfate (a detergent), 1.0 mM EDTA (a metal chelator), and 1.0 mM Tris (a buffer to maintain correct pH). The preservative is stable at room temperature for at least six months. A small volume of the liquid preservative is added to saliva (or other body fluids), the mixture is mixed by inversion, and then is left undisturbed at room temperature until the analysis is conducted. No other preservative has been identified that stabilizes saliva and other body fluids at room temperature for subsequent analyses.

This work was done by Duane L. Pierson of Johnson Space Center and Satish K. Mehta of EASI. MSC-25144-1

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