Validation of MALDI-MS imaging data of selected membrane lipids in murine brain with and without laser postionization by
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RESEARCH PAPER
Validation of MALDI-MS imaging data of selected membrane lipids in murine brain with and without laser postionization by quantitative nano-HPLC-MS using laser microdissection Fabian B. Eiersbrock 1 & Julian M. Orthen 1 & Jens Soltwisch 1,2 Received: 17 April 2020 / Revised: 8 June 2020 / Accepted: 14 July 2020 # The Author(s) 2020
Abstract MALDI mass spectrometry imaging (MALDI-MSI) is a widely used technique to map the spatial distribution of molecules in sectioned tissue. The technique is based on the systematic generation and analysis of ions from small sample volumes, each representing a single pixel of the investigated sample surface. Subsequently, mass spectrometric images for any recorded ion species can be generated by displaying the signal intensity at the coordinate of origin for each of these pixels. Although easily equalized, these recorded signal intensities, however, are not necessarily a good measure for the underlying amount of analyte and care has to be taken in the interpretation of MALDI-MSI data. Physical and chemical properties that define the analyte molecules’ adjacencies in the tissue largely influence the local extraction and ionization efficiencies, possibly leading to strong variations in signal intensity response. Here, we inspect the validity of signal intensity distributions recorded from murine cerebellum as a measure for the underlying molar distributions. Based on segmentation derived from MALDI-MSI measurements, laser microdissection (LMD) was used to cut out regions of interest with a homogenous signal intensity. The molar concentration of six exemplary selected membrane lipids from different lipid classes in these tissue regions was determined using quantitative nano-HPLC-ESI-MS. Comparison of molar concentrations and signal intensity revealed strong deviations between underlying concentration and the distribution suggested by MSI data. Determined signal intensity response factors strongly depend on tissue type and lipid species. Keywords MALDI . Mass spectrometry imaging . Laser postionization . MALDI-2 . Quantification . Signal intensity response . Laser microdissection . Nano-HILIC-nano-ESI-MS . Lipids
Introduction Combining the analytical benefits of mass spectrometric analysis with spatial information, mass spectrometry imaging (MSI) has evolved into an important analytical tool in a wide Fabian Eiersbrock and Julian Orthen contributed equally to this work. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00216-020-02818-y) contains supplementary material, which is available to authorized users. * Jens Soltwisch [email protected] 1
Institute of Hygiene, Westfälische Wilhelms-Universität Münster, Robert-Koch-Straße 41, 48149 Münster, Germany
2
Interdisciplinary Center for Clinical Research (IZKF), Westfälische Wilhelms-Universität Münster, Domagkstraße 3, 48149 Münster, Germany
field of application ranging from quality control in process management to the analysis of tissue samples in the life sciences
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