Laser ablation-inductively coupled plasma-mass spectrometry analysis reveals differences in chemotherapeutic drug distribution in surgically resected pleural mesothelioma.

AIMS: Pleural mesothelioma (PM) is a highly aggressive thoracic tumour with poor prognosis. Although reduced tissue drug accumulation is one of the key features of platinum (Pt) resistance, little is known about Pt distribution in human PM. METHODS: We assessed Pt levels of blood samples and surgically resected specimens from 25 PM patients who had received neoadjuvant Pt-based chemotherapy (CHT). Pt levels and tissue distributions were measured by laser ablation-inductively coupled plasma-mass spectrometry and correlated with clinicopathological features. RESULTS: In surgically resected PM specimens, mean Pt levels of nontumourous (fibrotic) areas were significantly higher (vs tumourous regions, P = 0.0031). No major heterogeneity of Pt distribution was seen within the tumourous areas. Pt levels correlated neither with the microvessel area nor with apoptosis rate in the tumourous or nontumourous regions. A significant positive correlation was found between serum and both full tissue section and tumourous area mean Pt levels (r = 0.532, P = 0.006, 95% confidence interval [95% CI] 0.161-0.771 and r = 0.415, P = 0.039, 95% CI 0.011-0.702, respectively). Furthermore, a significant negative correlation was detected between serum Pt concentrations and elapsed time from the last cycle of CHT (r = -0.474, P = 0.017, 95% CI -0.738--0.084). Serum Pt levels correlated negatively with overall survival (OS) (P = 0.029). CONCLUSIONS: There are major differences in drug distribution between tumourous and nontumourous areas of PM specimens. Serum Pt levels significantly correlate with full section and tumourous area average Pt levels, elapsed time from the last CHT cycle, and OS. Further studies investigating clinicopathological factors that modulate tissue Pt concentration and distribution are warranted.

Multisensor Imaging-From Sample Preparation to Integrated Multimodal Interpretation of LA-ICPMS and MALDI MS Imaging Data.

Laterally resolved chemical analysis (chemical imaging) has increasingly attracted attention in the Life Sciences during the past years. While some developments have provided improvements in lateral resolution and speed of analysis, there is a trend toward the combination of two or more analysis techniques, so-called multisensor imaging, for providing deeper information into the biochemical processes within one sample. In this work, a human malignant pleural mesothelioma sample from a patient treated with cisplatin as a cytostatic agent has been analyzed using laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) and matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS). While LA-ICPMS was able to provide quantitative information on the platinum distribution along with the distribution of other elemental analytes in the tissue sample, MALDI MS could reveal full information on lipid distributions, as both modes of polarity, negative and positive, were used for measurements. Tandem MS experiments verified the occurrence of distinct lipid classes. All imaging analyses were performed using a lateral resolution of 40 µm, providing information with excellent depth of details. By analyzing the very same tissue section, it was possible to perfectly correlate the obtained analyte distribution information in an evaluation approach comprising LA-ICPMS and MALDI MS data. Correlations between platinum, phosphorus, and lipid distributions were found by the use of advanced statistics. The present proof-of-principle study demonstrates the benefit of data combination for outcomes beyond one method imaging modality and highlights the value of advanced chemical imaging in the Life Sciences.

A comparison of sample preparation strategies for biological tissues and subsequent trace element analysis using LA-ICP-MS.

Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) is one of the most commonly applied methods for lateral trace element distribution analysis in medical studies. Many improvements of the technique regarding quantification and achievable lateral resolution have been achieved in the last years. Nevertheless, sample preparation is also of major importance and the optimal sample preparation strategy still has not been defined. While conventional histology knows a number of sample pre-treatment strategies, little is known about the effect of these approaches on the lateral distributions of elements and/or their quantities in tissues. The technique of formalin fixation and paraffin embedding (FFPE) has emerged as the gold standard in tissue preparation. However, the potential use for elemental distribution studies is questionable due to a large number of sample preparation steps. In this work, LA-ICP-MS was used to examine the applicability of the FFPE sample preparation approach for elemental distribution studies. Qualitative elemental distributions as well as quantitative concentrations in cryo-cut tissues as well as FFPE samples were compared. Results showed that some metals (especially Na and K) are severely affected by the FFPE process, whereas others (e.g., Mn, Ni) are less influenced. Based on these results, a general recommendation can be given: FFPE samples are completely unsuitable for the analysis of alkaline metals. When analyzing transition metals, FFPE samples can give comparable results to snap-frozen tissues. Graphical abstract Sample preparation strategies for biological tissues are compared with regard to the elemental distributions and average trace element concentrations.

Direct imaging of elemental distributions in tissue sections by laser ablation mass spectrometry.

We present a strategy for imaging of elements in biological tissues using laser ablation (LA) mass spectrometry (MS), which was compared to laser ablation inductively coupled plasma (LA-ICP) MS. Both methods were adopted for quantitative imaging of elements in mouse kidney, as well as traumatic brain injury model tissue sections. MS imaging (MSI) employing LA provides quantitative data by comparing signal abundances of sodium from tissues to those obtained by imaging quantitation calibration standards of the target element applied to adjacent control tissue sections. LA-ICP MSI provided quantitative data for several essential elements in both brain and kidney tissue sections using a dried-droplet approach. Both methods were used to image a rat model of traumatic brain injury, revealing accumulations of sodium and calcium in the impact area and its peripheral regions. LA MSI is shown to be a viable option for quantitative imaging of specific elements in biological tissue sections.

Identification of mumps virus protein and lipid composition by mass spectrometry.

BACKGROUND: Mumps virus is a negative-sense, single stranded RNA virus consisting of a ribonucleocapsid core enveloped by a lipid membrane derived from host cell, which causes mumps disease preventable by vaccination. Since virus lipid envelope and glycosylation pattern are not encoded by the virus but dependent on the host cell at least to some extent, the aim of this work was to analyse L-Zagreb (L-Zg) mumps virus lipids and proteins derived from two cell types; Vero and chicken embryo fibroblasts (CEF). Jeryl Lynn 5 (JL5) mumps strain lipids were also analysed. METHODS: Virus lipids were isolated by organic phase extraction and subjected to 2D-high performance thin layer chromatography followed by lipid extraction and identification by matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS). Virus samples were also subjected to gel electrophoresis under denaturating conditions and protein bands were excised, in-gel trypsinized and identified by MS as well as tandem MS. RESULTS: Results showed that lipids of both mumps virus strains derived from Vero cells contained complex glycolipids with up to five monosaccharide units whereas the lipid pattern of mumps virus derived from CEF was less complex. Mumps virus was found to contain expected structural proteins with exception of fusion (F) protein which was not detected but on the other hand, V protein was detected. Most interesting finding related to the mumps proteins is the detection of several forms of nucleoprotein (NP), some of which appear to be C-terminally truncated. CONCLUSIONS: Differences found in lipid and protein content of mumps virus demonstrated the importance of detailed biochemical characterization of mumps virus and the methodology described here could provide a means for a more comprehensive quality control in vaccine production.

Recent advances in quantitative LA-ICP-MS analysis: challenges and solutions in the life sciences and environmental chemistry.

Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) is a widely accepted method for direct sampling of solid materials for trace elemental analysis. The number of reported applications is high and the application range is broad; besides geochemistry, LA-ICP-MS is mostly used in environmental chemistry and the life sciences. This review focuses on the application of LA-ICP-MS for quantification of trace elements in environmental, biological, and medical samples. The fundamental problems of LA-ICP-MS, such as sample-dependent ablation behavior and elemental fractionation, can be even more pronounced in environmental and life science applications as a result of the large variety of sample types and conditions. Besides variations in composition, the range of available sample states is highly diverse, including powders (e.g., soil samples, fly ash), hard tissues (e.g., bones, teeth), soft tissues (e.g., plants, tissue thin-cuts), or liquid samples (e.g., whole blood). Within this article, quantification approaches that have been proposed in the past are critically discussed and compared regarding the results obtained in the applications described. Although a large variety of sample types is discussed within this article, the quantification approaches used are similar for many analytical questions and have only been adapted to the specific questions. Nevertheless, none of them has proven to be a universally applicable method.

Application of gold thin-films for internal standardization in LA-ICP-MS imaging experiments.

LA-ICP-MS imaging experiments are of growing interest within the field of biosciences. Revealing the distributions of major components as well as trace elements in biological samples can help to understand fundamental biological processes. However, highly variable sample conditions and changing instrumental parameters during measurement time aggravate reliable quantification especially in biological tissues. Normally matrix matched standards used for calibration are scarcely available and the manufacturing process thereof is rather complicated. Thus most experiments reported in the literature only delivered qualitative information on the analyte distributions. The use of appropriate internal standards facilitates the preparation of calibrations even without the utilization of matrix-matched standards. In the presented work an approach for providing reliable quantitative bio-images is proposed using gold thin-layers as an internal standard and patterns printed with commercially available inkjet printers as standards. The method development is based on copper from blue ink as the element of interest. It could be shown that gold standardization compensates instrumental drifts, matrix related ablation differences and day-to-day signal changes. Not only was the quality of the obtained images improved by gold standardization; while the relative standard deviation of the measurements was around 15% before standardization it could be decreased to less than 5% by gold standardization. Also quantitative information could be obtained for samples with unknown analyte concentrations. Depending on the used beam diameter limits of detection in the range of some hundreds ng g(-1) were achieved. The presented method is a promising and easy-to-handle alternative to matrix matched standards for signal quantification.

Online-LASIL: Laser Ablation of Solid Samples in Liquid with online-coupled ICP-OES detection for direct determination of the stoichiometry of complex metal oxide thin layers.

Advanced materials such as complex metal oxides are used in a wide range of applications and have further promising perspectives in the form of thin films. The exact chemical composition essentially influences the electronic properties of these materials which makes correct assessment of their composition necessary. However, due to high chemical resistance and in the case of thin films low absolute analyte amounts, this procedure is in most cases not straightforward and extremely time-demanding. Commonly applied techniques either lack in ease of use (i.e., solution-based analysis with preceding sample dissolution), or adequately accurate quantification (i.e., solid sampling techniques). An analysis approach which combines the beneficial aspects of solution-based analysis as well as direct solid sampling is Laser Ablation of a Sample in Liquid (LASIL). In this work, it is shown that the analysis of major as well as minor sample constituents is possible using a novel online-LASIL setup, allowing sample analysis without manual sample handling after placing it in an ablation chamber. Strontium titanate (STO) thin layers with different compositions were analyzed in the course of this study. Precision of the newly developed online-LASIL method is comparable to conventional wet chemical approaches. With only about 15-20 min required for the analysis per sample, time demand is significantly reduced compared to often necessary fusion procedures lasting multiple hours.

Interface Instability of Fe-Stabilized Li7La3Zr2O12 versus Li Metal.

The interface stability versus Li represents a major challenge in the development of next-generation all-solid-state batteries (ASSB), which take advantage of the inherently safe ceramic electrolytes. Cubic Li7La3Zr2O12 garnets represent the most promising electrolytes for this technology. The high interfacial impedance versus Li is, however, still a bottleneck toward future devices. Herein, we studied the electrochemical performance of Fe3+-stabilized Li7La3Zr2O12 (LLZO:Fe) versus Li metal and found a very high total conductivity of 1.1 mS cm-1 at room temperature but a very high area specific resistance of ∼1 kΩ cm2. After removing the Li metal electrode we observe a black surface coloration at the interface, which clearly indicates interfacial degradation. Raman- and nanosecond laser-induced breakdown spectroscopy reveals, thereafter, the formation of a 130 µm thick tetragonal LLZO interlayer and a significant Li deficiency of about 1-2 formula units toward the interface. This shows that cubic LLZO:Fe is not stable versus Li metal by forming a thick tetragonal LLZO interlayer causing high interfacial impedance.

Fourier Transform Infrared (FT-IR) and Laser Ablation Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) Imaging of Cerebral Ischemia: Combined Analysis of Rat Brain Thin Cuts Toward Improved Tissue Classification.

Microspectroscopic techniques are widely used to complement histological studies. Due to recent developments in the field of chemical imaging, combined chemical analysis has become attractive. This technique facilitates a deepened analysis compared to single techniques or side-by-side analysis. In this study, rat brains harvested one week after induction of photothrombotic stroke were investigated. Adjacent thin cuts from rats' brains were imaged using Fourier transform infrared (FT-IR) microspectroscopy and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The LA-ICP-MS data were normalized using an internal standard (a thin gold layer). The acquired hyperspectral data cubes were fused and subjected to multivariate analysis. Brain regions affected by stroke as well as unaffected gray and white matter were identified and classified using a model based on either partial least squares discriminant analysis (PLS-DA) or random decision forest (RDF) algorithms. The RDF algorithm demonstrated the best results for classification. Improved classification was observed in the case of fused data in comparison to individual data sets (either FT-IR or LA-ICP-MS). Variable importance analysis demonstrated that both molecular and elemental content contribute to the improved RDF classification. Univariate spectral analysis identified biochemical properties of the assigned tissue types. Classification of multisensor hyperspectral data sets using an RDF algorithm allows access to a novel and in-depth understanding of biochemical processes and solid chemical allocation of different brain regions.

Application of dried-droplets deposited on pre-cut filter paper disks for quantitative LA-ICP-MS imaging of biologically relevant minor and trace elements in tissue samples.

In this work, a novel calibration approach for minor and trace element quantification in LA-ICP-MS imaging of biological tissues is presented. Droplets of aqueous standard solutions are deposited onto pre-cut pieces of filter paper, allowed to dry, and sputtered with a thin gold layer for use as pseudo-internal standard. Analysis of the standards using LA-ICP-MS is performed using radial line-scans across the filters. In contrast to conventionally used preparation of matrix-matched tissue standards, the dried-droplet approach offers a variety of advantages: The standards are easy to prepare, no characterization of the standards using acid digestion is required, no handling of biological materials is necessary, and the concentration range, as well the number of investigated analytes is almost unlimited. The proposed quantification method has been verified using homogenized tissue standards with known analyte concentrations before being applied to a human malignant mesothelioma biopsy from a patient who had not received any chemotherapeutic treatment. Elemental distribution images were acquired at a lateral resolution of 40 µm per pixel, limits of detection ranging from 0.1 µg g(-1) (Mn, Ni, Cu, Zn) to 13.2 µg g(-1) (K) were reached.

Characterization of recombinant human diamine oxidase (rhDAO) produced in Chinese Hamster Ovary (CHO) cells.

Human diamine oxidase (hDAO) efficiently degrades polyamines and histamine. Reduced enzyme activities might cause complications during pregnancy and be involved in histamine intolerance. So far hDAO has been characterized after isolation from either native sources or the heterologous production in insect cells. Accessibility to human enzyme is limited and insect cells produce non-human glycosylation patterns that may alter its biochemical properties. We present the heterologous expression of hDAO in Chinese Hamster Ovary (CHO) cells and a three step purification protocol. Analysis of metal content using ICP-MS revealed that 93% of the active sites were occupied by copper. Topaquinone (TPQ) cofactor content was determined using phenylhydrazine titration. Ninety-four percent of DAO molecules contained TPQ and therefore the copper content at the active site was indirectly confirmed. Mass spectrometric analysis was conducted to verify sequence integrity of the protein and to assess the glycosylation profile. Electronic circular dichroism and UV-vis spectra data were used to characterize structural properties. The substrate preference and kinetic parameters were in accordance with previous publications. The establishment of a recombinant production system for hDAO enables us to generate decent amounts of protein with negligible impurities to address new scientific questions.