Human Salivary Protein Analysis Using RNAProSAL™, PureSAL™, and the Passive Drooling Method in a Pakistani Population

Abstract

Objectives: The aim of the current study was to carry out a preliminary validation of devices for standardized collection of whole mouth fluid (WMF) in comparison to the passive drooling method for protein analysis in healthy subjects. Methods: A carefully designed sample collection/pretreatment protocol is crucial to the success of any saliva proteomics project. In this study WMF was collected from healthy volunteers (n=10, ages: 18-26 years). Individuals with any oral disease were excluded from the study group. In our study we evaluated the following collection methods; the classical passive drooling method (unstimulated whole saliva) and standardized tools for saliva collection [PureSAL™, and RNAProSAL™] from Oasis Diagnostics® Corporation [Vancouver WA, USA] (See Figures-1 and 2 below) (Chiang et al., 2015). For estimation of protein levels, we used the Bicinchoninic acid assay (BCA) protein assay kit (Thermo Fisher) (Krieg et al., 2005). Results: In the case of circle ‘c’ this showed a few spots that are much clearer in saliva samples collected using the PureSAL™ device. The noted differences may be observed due to the intrinsic properties of the RNAProSAL™ and PureSAL™ technologies (see Figure-3), which both use highly absorbent pad materials to collect saliva and act to remove a high percentage of mucinous material (>70%). The recovery of a highly purified sample is readily obtained by compression through a proprietary medium to clear potential interferences likely to cause problems with downstream assays. Conclusions: We concluded that passive drooling, which is a method that requires practice and is less desirable and more time consuming for participants, and also provides an unfiltered sample but these two devices provide a readily purified sample directly into a standard collection tube that is stabilized independently for immediate use or stored for long term storage pending analysis.