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Radiation dose is important in radiotherapy. Too little, and the treatment is not effective, too much causes radiation toxicity. A biochemical measurement of the effect of radiotherapy would be useful in personalisation of this treatment. This study evaluated changes in exhaled breath volatile organic compounds (VOC) associated with radiotherapy with thermal desorption gas chromatography mass-spectrometry followed by data processing and multivariate statistical analysis. Further the feasibility of adopting gas chromatography ion mobility spectrometry for radiotherapy point-of-care breath was assessed. A total of 62 participants provided 240 end-tidal 1 dm 3 breath samples before radiotherapy and at 1, 3, and 6 h post-exposure, that were analysed by thermal-desorption/gas-chromatography/quadrupole mass-spectrometry. Data were registered by retention-index and mass-spectra before multivariate statistical analyses identified candidate markers. A panel of sulfur containing compounds (thio-VOC) were observed to increase in concentration over the 6 h following irradiation. 3-methylthiophene (80 ng.m -3 to 790 ng.m -3 ) had the lowest abundance while 2-thiophenecarbaldehyde(380 ng.m -3 to 3.85 μg.m -3 ) the highest; note, exhaled 2-thiophenecarbaldehyde has not been observed previously. The putative tumour metabolite 2,4-dimethyl-1-heptene concentration reduced by an average of 73% over the same time. Statistical scoring based on the signal intensities thio-VOC and 3-methylthiophene appears to reflect individuals' responses to radiation exposure from radiotherapy. The thio-VOC are hypothesised to derive from glutathione and Maillard-based reactions and these are of interest as they are associated with radio-sensitivity. Further studies with continuous monitoring are needed to define the development of the breath biochemistry response to irradiation and to determine the optimum time to monitor breath for radiotherapy markers. Consequently, a single 0.5 cm 3 breath-sample gas chromatography-ion mobility approach was evaluated. The calibrated limit of detection for 3-methylthiophene was 10 μg.m -3 with a lower limit of the detector's response estimated to be 210 fg.s -1 ; the potential for a point-of-care radiation exposure study exists.

A complex profile of volatile organic compounds ("VOC"s) emanates from human skin, which is altered by changes in the body's metabolic or hormonal state, the external environment, and the bacterial species colonizing the skin surface. The aim of this study was to compare VOC profiles sampled from chronic leg wounds with those from asymptomatic skin. Five participants with chronic arterial leg ulcers were selected. VOC samples were obtained using polydimethylsilicone membranes ("skin-patch method") and analyzed by gas chromatography-ion trap mass spectrometry. Resultant data were analyzed using multivariate analysis and mass spectral matches were compared against the National Institute of Standards and Technology database. Principal component analysis showed differences in profiles obtained from healthy skin and boundary areas and between profiles from healthy skin and lesion samples (p<0.05). Partial least squares for discriminant analysis gave an average prediction accuracy of 73.3% (p<0.05). Mass spectral matching (verified against microbial swab results) identified unique VOCs associated with each sample area, wound bacterial colonization, and ingested medications. This study showcases a reproducible, robust, noninvasive methodology that is applicable in a clinical setting and may offer a new, hitherto unexplored, class of biochemical markers underpinning the metabolism of chronic wounds.

The rapid, accurate and non-invasive diagnosis of respiratory disease represents a challenge to clinicians, and the development of new treatments can be confounded by insufficient knowledge of lung disease phenotypes. Exhaled breath contains a complex mixture of volatile organic compounds (VOCs), some of which could potentially represent biomarkers for lung diseases. We have developed an adaptive sampling methodology for collecting concentrated samples of exhaled air from participants with impaired respiratory function, against which we employed two-stage thermal desorption gas chromatography-differential mobility spectrometry (GC-DMS) analysis, and showed that it was possible to discriminate between participants with and without chronic obstructive pulmonary disease (COPD). A 2.5 dm(3) volume of end tidal breath was collected onto adsorbent traps (Tenax TA/Carbotrap), from participants with severe COPD and healthy volunteers. Samples were thermally desorbed and analysed by GC-DMS, and the chromatograms analysed by univariate and multivariate analyses. Kruskal-Wallis ANOVA indicated several discriminatory (p < 0.01) signals, with good classification performance (receiver operator characteristic area up to 0.82). Partial least squares discriminant analysis using the full DMS chromatograms also gave excellent discrimination between groups (alpha = 19% and beta = 12.4%).