A Review of Analytical Techniques and Their Application in Disease Diagnosis in Breathomics and Salivaomics Research

Abstract

The application of metabolomics to biological samples has been a key focus in systems biology research, which is aimed at the development of rapid diagnostic methods and the creation of personalized medicine. More recently, there has been a strong focus towards this approach applied to non-invasively acquired samples, such as saliva and exhaled breath. The analysis of these biological samples, in conjunction with other sample types and traditional diagnostic tests, has resulted in faster and more reliable characterization of a range of health disorders and diseases. As the sampling process involved in collecting exhaled breath and saliva is non-intrusive as well as comparatively low-cost and uses a series of widely accepted methods, it provides researchers with easy access to the metabolites secreted by the human body. Owing to its accuracy and rapid nature, metabolomic analysis of saliva and breath (known as salivaomics and breathomics, respectively) is a rapidly growing field and has shown potential to be effective in detecting and diagnosing the early stages of numerous diseases and infections in preclinical studies. This review discusses the various collection and analyses methods currently applied in two of the least used non-invasive sample types in metabolomics, specifically their application in salivaomics and breathomics research. Some of the salient research completed in this field to date is also assessed and discussed in order to provide a basis to advocate their use and possible future scientific directions.

Exhaled breath analysis: a review of ‘breath-taking’ methods for off-line analysis

“…The concept behind breath metabolomics (also known as breathomics) is that the VOC profile in breath will be altered when a switch from a healthy to a pathological state occurs and this can be detected and potentially utilised for diagnosis and monitoring (Beale et al 2016). The origin of breath VOCs include the environment (termed exogenous), the host (endogenous), and also the microbiome (the microorganisms that inhabit the mouth, lung and gut) (Boots et al 2015; Bos et al 2013; Schulz and Dickschat 2007).…”

Volatile organic compound detection as a potential means of diagnosing cutaneous wound infections

“…The length of the columns used varies with longer columns providing better chromatographic resolution and maximum separation of analytes. Each compound is emitted from the column at different times with the mass spectrometer used to detect eluting compounds through compound ionization followed by measurement of the mass to charge ratio of each ion generating a unique mass spectrum for the compound . The major advantages of GC–MS are increased sensitivity and compound identification is greatly facilitated by the availability of extensive and easily searchable databases .…”

Volatile Organic Compound and Metabolite Signatures as Pathogen Identifiers and Biomarkers of Infectious Disease

“…Here we summarize the various methods used for VOC detection. The advantages and limitations associated with these techniques and instruments are summarized in Table 1, and reviewed in detail elsewhere (see [17,21,27,28]). …”

“…The class of volatile that can be detected by GC depends on the type of detector used. Examples include time of flight (TOF), plasma ionization, photoionization and electron capture detectors [17].…”

“…As such, when sampling saliva, it is essential to characterize the sample in terms of its location. Most studies utilizing saliva samples collect the whole saliva mixture comprised of all the various glandular saliva types produced in the mouth [17]. While the protein composition arising from each salivary gland is well characterized, the metabolite composition is not well understood.…”