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Abstract Several investigations have identified volatile organic compounds (VOCs) as potential biomarkers for the detection and identification of microbial contamination of metabolically active mammalian cell cultures. In this study, we showed that emitted VOCs discriminate between uncontaminated mesenchymal stromal cells (MSCs) and those contaminated with the bacteriumStaphylococcus epidermidisor fungusAspergillus Fumigatusseparately,in vitro, using a methodology based on an adapted cell culture and thermal desorption–gas chromatography–mass spectrometry. In addition, we elucidated a set of discriminatory volatile compounds from the MSC cultures and media alone across a time series experiment. Partial least squares–discriminant analysis-variable importance in projection confirmed putative identifications of 18, 16, and 26 VOCs that showed relevant changes in a bacterial, fungal, and universal pathogen model, respectively, with an accuracy of 100% in the fungal model. Among these metabolites, octane, 2,5,6-trimethyl- overlapped between the three groups. Furthermore, a total of 15 VOCs were found most relevant to cell culture expansion over three days based on cluster analysis. This novel study goes a step further in identifying distinct VOC signatures of MSCs contaminated withS. epidermidisorA. fumigatus, and in monitoring MSCs proliferation over time. This pilot study shows preliminary results that indicate that VOC headspace analysis could serve as a suitable, rapid, non-invasive, and non-destructive tool for the metabolic and growth monitoring of MSCs in a dynamic cell culture bioreactor system. 

Abstract Human skin is an important source of volatile organic compounds (VOCs) offering noninvasive methods to gain clinical metabolite information. This work was focused on the development of a skin sampling device based on a dynamic headspace sampling method with the addition of temperature to increase VOC metabolite recovery. The device preconcentrates skin VOC emissions onto a sorbent substrate, which can either be preserved for offline analysis or attached to a real time sensor downstream. In this work, skin VOC samples were analyzed offline using thermal desorption-gas chromatography-mass spectrometry. A list of 10 common skin VOCs was pre-selected to optimize parameters of sampling time, sampling temperature, and sorbent selection. Overall, this study highlights an effective skin VOC sampling technology with a heating dimension (40 °C, rather than 30 °C or no heating) with a sampling time of 15 min (rather than 5 or 30 mins) and onto Tenax TA sorbent (rather than PDMS), which collectively increases the recovery of compounds with lower vapor pressure and decreases the observed variability in skin VOC measurements. Finally, a list of 79 skin VOC compounds were detected and identified within a cohort of 20 young, healthy volunteers. 

Metabolically active cells emit volatile organic compounds (VOCs) that can be used in real time to non-invasively monitor the health of cell cultures. We utilized these naturally occurring VOCs in an adapted culture method to detect differences in culturing Chinese hamster ovary (CHO) cells with and without Staphylococcus epidermidis and Aspergillus fumigatus contaminations. The VOC emissions from the cell cultures were extracted and measured from the culture flask headspace using polydimethylsiloxane (PDMS)-coated Twisters, which were subjected to thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS) analysis. In our initial time points of 1 and 2 h, we detected VOC signatures that differentiated the cultures earlier than traditional plating techniques or visualization methods. Partial least squares-discriminant analysis (PLS-DA) models were built to differentiate the analytes from the CHO cells and S. epidermidis- and A. fumigatus-inoculated CHO cultures. A total of 41 compounds with a variable importance in projection (VIP) score greater than 1 was obtained across the models. Similarly, based on the PLS regression analyses to predict the cell concentration of S. epidermidis (R2 = 0.891) and A. fumigatus (R2 = 0.375), 15 and 20 relevant compounds were putatively identified, respectively; two known compounds overlapped between the two microbes. Some of the compounds were unidentified and future studies will deter- mine the relationship between the VOCs and the metabolic changes in contaminated cultures. 

Abstract Regional stream sediment surveys are an important exploration tool used in the search for concealed or partially concealed porphyry deposits. It is shown here that quartz contained in the coarse fraction of stream sediments can be used as an indicator mineral to supplement geochemical analyses conducted on the fine fraction, such as the measurement of the bulk cyanide leach extractable gold content. A method is proposed that allows separation of quartz grains from the coarse rejects of stream sediment samples to prepare grain mounts for petrographic analysis. Based on optical cathodoluminescence microscopy and fluid inclusion petrography, the number of porphyry quartz grains in each grain mount is then identified. Case studies conducted at Vert de Gris in Haiti and Hides Creek in Papua New Guinea show that porphyry quartz grains could be confidently identified in sediments in the catchment areas of both porphyries. Because the cost of microscopic analysis of quartz is small compared to the expense of sampling and geochemical analysis, the developed technique could be routinely used in large greenfield exploration programs. It is envisaged here that petrographic analysis of quartz grains can contribute valuable information for prioritization of targets defined based on their geochemical signatures. 

Dehydrogenation of the ligand backbone of a bis(amido)bis(phosphine) Co complex is achieved through hydrogen atom abstraction. The new unsaturated backbone of the tetradentate ligand renders the ligand in the resulting Co complex redox-active.