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Microneedles have been demonstrated to be a minimally invasive technique for sampling dermal interstitial fluid (ISF). Shotgun quantitative proteomics has already identified hundreds of proteins in ISF and quantitatively compared the proteome to matching serum and plasma. Interstitial fluid was determined to be a viable minimally invasive alternative to blood-derived fluids. In this communication, we re-examined the proteomic data from previous work to determine the diversity of immunoglobulins present compared with serum and plasma. Similar to our previous findings regarding the proteomic content across fluid types, ISF had a similar composition of IgG, IgA, IgD, and IgE antibodies as plasma or serum and lower quantities of IgM, which reflects the relative concentrations of dermal tissue T-cell and B-cell populations, indicating that the Ig's were likely locally derived. This work has significant implications for the utility of measuring Ig's in ISF for the clinical diagnosis of immunological diseases and skin infections. Data are available via ProteomeXchange with identifier PXD012658.

Derivatization of paper spray substrates was shown to greatly increase the time for analysis of CWAs. This technique, combined with the vapor phase capture stage outlined previously, allows for rapid, quantitative CWA detection by paper spray ionization with little or no sample preparation.

The inhibition of acetylcholinesterase is regarded as the primary toxic mechanism of action for chemical warfare agents. Recently, there have been numerous reports suggesting that metabolic processes could significantly contribute to toxicity. As such, we applied a multi-omics pipeline to generate a detailed cascade of molecular events temporally occurring in guinea pigs exposed to VX. Proteomic and metabolomic profiling resulted in the identification of several enzymes and metabolic precursors involved in glycolysis and the TCA cycle. All lines of experimental evidence indicated that there was a blockade of the TCA cycle at isocitrate dehydrogenase 2, which converts isocitrate to α-ketoglutarate. Using a primary beating cardiomyocyte cell model, we were able to determine that the supplementation of α-ketoglutarate subsequently rescued cells from the acute effects of VX poisoning. This study highlights the broad impacts that VX has and how understanding these mechanisms could result in new therapeutics such as α-ketoglutarate.

Currently, all assays measuring acetylcholinesterase (AChE) activity following a suspected nerve agent exposure leverage methodologies that fail to identify the agent. This limits the overall effectiveness and ability to administer proper countermeasures. As such, there is an urgent need to identify novel, rapid, and more comprehensive approaches to establish AChE activity, including identification of the toxicant. Paper spray mass spectrometry was used to monitor the activity of acetylcholinesterase, both in-solution and on modified hydrophobic paper surface. Hydrophobic paper surfaces were prepared using vaporized trichloro(3,3,3-trifluoropropyl)silane. In both approaches, mixtures of diluted human whole blood with and without VX were mixed with a non-endogenous AChE specific substrate, 1,1-dimethyl-4-acetylthiomethylpiperidinium (MATP+). Formation of the cleaved MATP+ product was monitored over time and compared to MATP+ to determine relative AChE activity. This on-substrate assay was effective at determining AChE activity and identifying the toxicant; however, determination of AChE activity in-solution proceeded at a slower rate. The on-substrate assay serves as a pioneering example of an enzymatic reaction occurring on the surface of a paper spray ionization ticket. This work broadens the range of applications relating to paper spray ionization-based clinical diagnostic assays. Graphical Abstractᅟ Electronic supplementary materialThe online version of this article (10.1007/s13361-018-2072-1) contains supplementary material, which is available to authorized users.