Evaluation of lipid coverage and high spatial resolution MALDI-imaging capabilities of oversampling combined with laser post-ionisation

Andrew P. Bowman, Jeroen F. J. Bogie, Jerome J. A. Hendriks, Mansour Haidar, Mikhail Belov, Ron M. A. Heeren, Shane R. Ellis*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

42 Citations (Web of Science)

Abstract

Matrix-assisted laser desorption/ionisation-mass spectrometry imaging (MALDI-MSI) is a powerful technique for visualising the spatial locations of lipids in biological tissues. However, a major challenge in interpreting the biological significance of local lipid compositions and distributions detected using MALDI-MSI is the difficulty in associating spectra with cellular lipid metabolism within the tissue. By-and-large this is due to the typically limited spatial resolution of MALDI-MSI (30-100 mu m) meaning individual spectra represent the average spectrum acquired from multiple adjacent cells, each potentially possessing a unique lipid composition and biological function. The use of oversampling is one promising approach to decrease the sampling area and improve the spatial resolution in MALDI-MSI, but it can suffer from a dramatically decreased sensitivity. In this work we overcome these challenges through the coupling of oversampling MALDI-MSI with laser post-ionisation (MALDI-2). We demonstrate the ability to acquire rich lipid spectra from pixels as small as 6 mu m, equivalent to or smaller than the size of typical mammalian cells. Coupled with an approach for automated lipid identification, it is shown that MALDI-2 combined with oversampling at 6 mu m pixel size can detect up to three times more lipids and many more lipid classes than even conventional MALDI at 20 mu m resolution in the positive-ion mode. Applying this to mouse kidney and human brain tissue containing active multiple sclerosis lesions, where 74 and 147 unique lipids are identified, respectively, the localisation of lipid signals to individual tubuli within the kidney and lipid droplets with lesion-specific macrophages is demonstrated.

Original languageEnglish
Pages (from-to)2277-2289
Number of pages13
JournalAnalytical and Bioanalytical Chemistry
Volume412
Issue number10
Early online date26 Dec 2019
DOIs
Publication statusPublished - Apr 2020

Keywords

  • Mass spectrometry imaging
  • MALDI
  • Lipids
  • Kidney
  • Brain
  • Multiple sclerosis
  • MASS-SPECTROMETRY
  • ELECTROSPRAY-IONIZATION
  • DESORPTION IONIZATION
  • ELEVATED PRESSURE
  • WHITE-MATTER
  • TISSUE
  • BRAIN
  • SPHINGOLIPIDS
  • SUBLIMATION
  • SECTIONS

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