Biomedical Engineering Reference
In-Depth Information
22.2.1.5.2
RNA
RNA can be isolated directly from saliva using a number of available “Salivary RNA Isolation”
kits sold by Qiagen, GE Healthcare, Life Technologies, and others. Although the procedure to iso-
late RNA by this method is time consuming and costly, saliva has become a “trusted” medium for
RNA research and development. There are no current tools available for direct RNA isolation;
however, there are tools in development that will be useful for this purpose. Novel tools should be
available within 1
2 years.
22.2.1.6
Applications of saliva in proteomics
Human saliva consists of a large number of proteins and peptides (the salivary proteome and pepti-
dome)
[81,82]
that aids in maintaining oral homeostasis. Unlike the plasma proteome, the saliva
proteome is highly susceptible to a variety of physiological and biochemical processes, and this
presents a challenge for clinical salivary proteomics
[29,83,84]
. The dynamic range of proteins in
saliva is another challenge. For instance, the abundant
-amylase in saliva is present at mg/mL con-
centrations, while the IL-6 and IL-8 cytokines of potential clinical relevance are present only at
concentrations of pg/mL
[85]
. The saliva proteome also changes as a function of age. A loss of sali-
vary acinar cell function was documented in healthy adults as a consequence of aging
[86,87]
,
while salivary production remained age stable in healthy adults. Such effects must be carefully con-
sidered in the development of salivary diagnostic assays, primarily by inclusion of appropriate
control groups in assay development and validation.
α
22.2.2
Saliva research update
Saliva research expands from infectious disease detection, to dental research to assess gum dis-
eases, to psychology and forensic sciences. As of today, a number of researchers are focusing on
developing techniques and tools to discern the biomolecular composition of saliva with the aim of
facilitating clinical translation. Saliva collection is a crucial step in the utilization of saliva for clini-
cal purposes, so it is very important that saliva collection technique should not influence down-
stream applications. There are commercially available saliva collection devices suited for both the
life science research as well as for diagnostic purposes, such as DNA Genotek (
www.dnagenotek.
com
); Salimetrics oral
swabs
Versi
(
http://www.4saliva.com
); OraSure Technologies OraSure Oral
Fluid Collection Device (
http://www.orasure.com
)
; Cozart
SAL
s
, and DNA
SAL
t
s
drugs of abuse collection devices
(
http://www.concateno.com
), Immunalysis Quantisal
Saliva Collection Device; and the Greiner
Bio-One Saliva Collection System (
http://www.gbo.com
)
[4]
. These saliva sample collection tech-
nologies assist in obtaining either unstimulated or stimulated saliva.
Saliva collection procedures differ based on the type of saliva that one is interested in collecting.
As an example, for ductal secretion collections, one can use Carlson
t
Crittenden cup
[88,89]
over the
orifice of the Stenson's duct
[90]
. However, these methods are invasive and forfeit the noninvasive
advantage of saliva for clinical use. It is important to determine experimentally which collection
device is suited for a particular application before commencing any clinical trials. Standardization of
saliva collection methods is also vital in translating saliva research from the lab to the clinic
[91]
.
