Evidence of endogenous volatile organic compounds as biomarkers of diseases in alveolar breath.

The effect of oxygen on markers of oxidative stress has been partially elucidated. Volatile organic compounds (VOCs) are created during the oxidative burst and excreted in the human alveolar breath, which indeed contains biomarkers. A general concept including collection, separation, detection and clinical biomakers validation is presented in this article: (i) a method for the collection and GC-MS of halogenated VOCs in human alveolar breath is described: a transportable apparatus which sampled specifically alveolar breath; the VOCs were captured in a thermal desorption tube, Carbotrap 200® and each sample was thermally desorbed from the trap in an automated GC-MS apparatus; (ii) the inhibitory effects of halogenated alkanes on mitochondria are suspected likely to fight against oxidative stress deleterious reactions; (iii) two-dimensional gas chromatography occurs by the repeated and re-injection of effluent from one chromatographic column into a second column of orthogonal phase. A new commercial GCxGC system is presented; it is accomplished with a dual-stage, quad-jet thermal modulator positioned between the two columns; (iv) the affinity-based sensors usually used in connection with the GCxGC system face a difficulty to take into account different biases coming from different sources of drifting. Compared to other affinity-based sensing modes like electrical ones, gravimetric sensors enable a better decoupling. Nano Electro Mechanical Systems (NEMS)-based resonators are a particular type of gravimetric gas sensors. They are coated with a sensitive layer of polymer where gases of interest present in the atmosphere adsorb, generating an additional mass load which is measured through a frequency shift; (v) examination of exhaled breath has the potential to change the existing routine approaches in human medicine. Breath sampling to identify volatile biomarkers in diseases has been proposed in several respiratory diseases. Several VOCs have been identified in these patients by GC-MS. However, the use of traditional analytical instruments such as GC-MS to detect biomarkers of diseases has not become a routine for clinical applications. Consequently the electronic nose was the logical instrument of choice for disease diagnosis due to the capability of identifying complex mixtures of VOCs (as a whole) within sampled air using pattern-recognition algorithms.