39 research outputs found

    Characterization of Polymer Membranes by MALDI Mass-Spectrometric Imaging Techniques

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    For physical and chemical characterization of polymers, a wide range of analytical methods is available. Techniques like NMR and X-ray are often combined for a detailed characterization of polymers used in medical applications. Over the past few years, MALDI mass-spectrometry has been developed as a powerful tool for space-resolved analysis, not least because of its mass accuracy and high sensitivity. MALDI imaging techniques combine the potential of mass-spectrometric analysis with imaging as additional spatial information. MALDI imaging enables the visualization of localization and distribution of biomolecules, chemical compounds, and other molecules on different surfaces. In this study, surfaces of polymeric dialyzer membranes, consisting of polysulfone (PS) and polyvinylpyrrolidone (PVP), were investigated, regarding chemical structure and the compound’s distribution. Flat membranes as well as hollow fiber membranes were analyzed by MALDI imaging. First, analysis parameters like laser intensity and laser raster step size (spatial resolution in resulting image) were established in accordance with polymer’s characteristics. According to the manufacturing process, luminal and abluminal membrane surfaces are characterized by differences in chemical composition and physical characteristics. The MALDI imaging demonstrated that the abluminal membrane surface consists more of polysulfone than polyvinylpyrrolidone, and the luminal membrane surface displayed more PVP than PS. The addition of PVP as hydrophilic modifier to polysulfone-based membranes increases the biocompatibility of the dialysis membranes. The analysis of polymer distribution is a relevant feature for characterization of dialysis membranes. In conclusion, MALDI imaging is a powerful technique for polymer membrane analysis, regarding not only detection and identification of polymers but also localization and distribution in membrane surfaces

    Signal intensities of exemplary analytes that accumulate during hemodialysis.

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    <p>Signal intensities of analytes P9 and P11 in 28 healthy controls, 26 patients with chronic renal failure (CRF) stage 2–4 according to K/DOQI-criteria, 28 patients with end-stage renal disease (ESRD, CRF stage 5D) prior to and 22 after hemodialysis. Signal intensities were tested for statistical significance by two-tailed t-tests; *p<0.05, **p<0.01, ***p<0.001.</p

    Signal intensities of exemplary analytes that accumulate with decreasing renal function and are eliminated by dialysis.

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    <p>Figures A–C present signal intensities of exemplary analytes P1–P3 and Figure D the sum of the signal intensities of the five analytes that accumulate with decreasing function and are eliminated by dialysis (P1–P5) in 28 healthy controls, 26 patients with chronic renal failure (CRF) stage 2–4 according to K/DOQI-criteria, 28 patients with end-stage renal disease (ESRD, CRF stage 5D) prior to and 22 after hemodialysis. Signal intensities were tested for statistical significance by two-tailed t-tests; *p<0.05, **p<0.01, ***p<0.001.</p

    Receiver-operating-characteristic (ROC) curves to distinguish different stages of renal failure.

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    <p>ROC curves for the sum of the signal intensities of hydroxyacetone, hydroxy-2-butanone, ammonia, 0.5468–17.0, and 0.5985–55.6 in differentiating (A) healthy subjects and patients with chronic renal failure (CRF) corresponding to an eGFR of 10–59 ml/min per 1.73 m<sup>2</sup> (AUC 0.76), (B) healthy subjects and patients with endstage renal disease (ESRD, AUC 0.83), and (C) healthy subjects and all patients with impaired renal function (CRF and ESRD; AUC 0.80).</p

    Scheme of an ion mobility spectrometer (MCC/IMS).

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    <p>The multi-capillary column (MCC) provides a preseparation of the molecules in the gas phase. In the ionization chamber proton transfer from the reactant ions to the analyte molecules takes place, thus forming protonated analyte ions. The drift time of the ions in the electric field depends on size and shape of the analytes. The retention time in the MCC and mobility in the IMS characterize the identity of the analyte. The intensity of the signal is a measure of the analyte's concentration.</p

    Representative multi-capillary column/ion mobility spectra (MCC/IMS) of breath samples.

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    <p>Breath sample of (A) a healthy adult, (B) an end-stage renal disease proband before and (C) after hemodialysis treatment. Areas of interest are marked and labeled by numbers. Substances corresponding to these numbers are given in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0046258#pone-0046258-t002" target="_blank">Table 2</a>. Signal intensity is coded by colours (yellow: very high; red high, blue: moderate, white: no signal).</p

    Reduced numbers of SMCs in transplanted Cx3cr1<sup>-/-</sup>Apoe<sup>-/-</sup> aortic plaques.

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    <p><i>Apoe</i><sup>-/-</sup> mice were transplanted with <i>Apoe</i><sup>-/-</sup> aortic segments (n = 4, <i>Apoe</i><sup>-/-</sup> > <i>Apoe</i><sup>-/-</sup>) or <i>Cx3cr1</i><sup><i>-/-</i></sup><i>Apoe</i><sup>-/-</sup> aortic segments (n = 5, <i>Cx3cr1</i><sup><i>-/-</i></sup> > <i>Apoe</i><sup>-/-</sup>), and <i>Cx3cr1</i><sup><i>-/-</i></sup><i>Apoe</i><sup>-/-</sup> mice were transplanted with <i>Apoe</i><sup>-/-</sup> aortic segments (n = 5, <i>Apoe</i><sup>-/-</sup> > <i>cx3cr</i>1<sup>-/-</sup>) and placed on a high fat diet for 4 weeks. Immunohistochemistry and quantification of (A) SMCs (alpha-Smooth Muscle Actin staining, x20, red) and (B) macrophages (MAC2, x20, green) in plaques of the transplanted aortic segment. Counterstaining with DAPI (blue) is showed in each images in insert. *p<0.05, Scale bars 100 μm.</p

    Reduced plaque size after transplantation of Cx3cr1<sup>-/-</sup>Apoe<sup>-/-</sup> aortas into Apoe<sup>-/-</sup> mice.

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    <p><i>Apoe</i><sup>-/-</sup> mice were transplanted with <i>Apoe</i><sup>-/-</sup> aortic segments (n = 4, <i>Apoe</i><sup>-/-</sup> > <i>Apoe</i><sup>-/-</sup>) or <i>Cx3cr</i>1<sup>-/-</sup><i>Apoe</i><sup>-/-</sup> aortic segments (n = 5, <i>Cx3cr</i>1<sup>-/-</sup> > <i>Apoe</i><sup>-/-</sup>), and <i>Cx3cr</i>1<sup>-/-</sup><i>Apoe</i><sup>-/-</sup> mice were transplanted with <i>Apoe</i><sup>-/-</sup> aortic segments (n = 5, <i>Apoe</i><sup>-/-</sup> > <i>Cx3cr</i>1<sup>-/-</sup>) and placed on a high fat diet for 4 weeks. Atherosclerotic plaques were analysed in H&E stained sections through the transplanted segment. Quantification of plaque area and representative sections (x20) are shown. *p<0.05, Scale bars 100 μm.</p

    Morphological pictures of HUVEC/HUASMC co-cultures upon physiological FSS conditions.

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    <p>(<b>A</b>) Scanning electron microscopy picture of the homogenously colonized inside of a hollow fiber with confluently grown and characteristically cobblestone shaped human primary endothelial cells upon the application of low laminar FSS (0.1 N/m<sup>2</sup>) for 24 h (magnification: 1∶500). (<b>B</b>) Scanning electron microscopy picture of HUASMCs on the hollow fiber outside with their typical cell cytoskeletal structure and morphology upon 0.1 N/m<sup>2</sup> applied for 24 h (magnification: 1∶400). (<b>C</b>) Confocal microscopic immunolocalization of Cadherin-5 in co-cultivated HUVECs exposed to low laminar FSS (0.1 N/m<sup>2</sup>) over a period of five days (magnification: 1∶400). (<b>D</b>)Cadherin-5 in HUVECs upon high laminar FSS (3 N/m<sup>2</sup>) (magnification: 1∶400). (<b>E</b>) Confocal microscopic immunolocalization of α-smooth-muscle-actin in co-cultivated HUASMCs upon 3 N/m<sup>2</sup> luminally applied for a five day period (magnification: 1∶400). (<b>F</b>) α-smooth-muscle-actin in co-cultivated HUASMCs upon high laminar FSS (3 N/m<sup>2</sup>) (magnification: 1∶400).</p
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