Sampling and characterisation of volatile organic compound profiles in human saliva using a polydimethylsiloxane coupon placed within the oral cavity

Abstract

Evaluation of published methods reveals that existing methods for saliva sampling do not address the physical-chemical attributes of volatile organic compounds (VOCs). This study describes and presents evidence for adopting in situ sampling of salivary VOCs directly from the oral cavity using a polydimethylsiloxane (PDMS) based sampler. In vitro studies indicated that the vapour pressure of analytes was a factor in both the recovery of analytes and the precision of the recovery. The highest recoveries were observed for VOCs with the lowest vapour pressures, for example 5-nonanol (vapour pressure (P v ) ¼ 14 Pa) recoveries were approximately 20 times greater than those observed for octane (P v ¼ 1726 Pa). Similarly, relative standard deviations reduced with vapour pressure, with the RSD for 5-nonanol responses observed to be 2.7% when compared to RSD ¼ 26% for octane. Evaluation of VOCs recovered from 6 in vivo samples indicated that VOC concentrations in saliva may follow lognormal distributions; log-normal RSDs falling between 4.4% and 18.2% across the range of volatilities encountered. Increasing sampling time from 1 to 30 minutes indicated that the recovery of VOC into the sampler was affected by interaction between different physical-chemical properties and biogenic flux. A sampling time of 10 min was found to offer an acceptable compromise that enabled a representative sample to be acquired for the widest range of observed VOC behaviours with the sampler. The potential to 'tune' the sampling protocol for targeted analysis based on these factors was also noted. Comparison with passive drool saliva collection revealed up to 10 5 enhancement with reduced variability compared to drooled samples. This approach to in situ saliva sampling appears to have significant analytical utility for studying volatile signatures in humans.

Hybrid Volatolomics and Disease Detection

“…[66b,d] Nevertheless,i ts hould be stressed that, apart from blood VOCs,s aliva can potentially contain VOCs resulting from serum, gingival exudate,t he nasal cavity,g astrointestinal reflux, food debris,o ral cavity microorganisms,c ommercial products,a nd environmental pollution. [68]…”

Microfluidic optoelectronic sensor for salivary diagnostics of stomach cancer

“…Salivary diagnostics is much more convenient than biopsy or blood test: sample collection is simple, non-invasive and, therefore, not painful (Martin et al, 2012;Soini et al, 2010;Streckfus and Bigler, 2002). With respect to the gastric cancer screening, saliva is commonly analyzed for the presence of abnormal genetic material, or of specific biomarkers, which are detected by analyte-specific interactions using immunoassay arrays (Ivnitski et al, 2004;Jokerst et al, 2009;Tan et al, 2008).…”

A rapid and non-invasive method to determine toxic levels of alcohols and γ -hydroxybutyric acid in saliva samples by gas chromatography–differential mobility spectrometry

“…Further, obtaining a passive drool sample requires significantly more 319 patient / participant training and compliance than placing a small rod under their 320 tongue and as such is likely to be a more practical approach to working with 321 patients/participants who may have analytes at levels high enough to be a cause of 322 concern for their safety and welfare [13]. Nevertheless the adoption of a passive 323 drooled-saliva approach enabled a matrix that approximated the intended sampling 324 conditions to be acquired safely and practicably.…”

“…A 109 chaperone, of the same gender as the participant, was present during sample 110 collection and access was restricted to only those researchers and participants 111 involved in the sampling process. After an introduction to the study the participants 112 were familiarised with the passive drool approach that was used to obtain a sample 113 of their saliva [13], before proceeding to provide approximately 10 cm 3 of saliva. 114…”

“…The current work sought to extend the earlier TD-GC-DMS study to include a semi-86 quantitative diagnostic screen of alcohol toxicants and GHB based on a non-87 invasive saliva sampling methodology and establish if direct extraction from saliva 88 to a polydimethylsilicone coupon [13] with recovery and analysis by TD-GC-DMS was 89 feasible. The DMS platform was chosen as this technique has been demonstrated 90 to be effective for the rapid, robust and sensitive detection and quantitation of 91 alcohols in low resource settings [14].…”