(CO2)n+, (H2O)n+, and (H2O)n+ (CO2) gas cluster ion beam secondary ion mass spectrometry: analysis of lipid extracts, cells, and Alzheimer\u2019s model mouse brain tissue

Kelly Dimovska Nilsson,John S Fletcher,Ibrahim Kaya,Anthi Karagianni,Marcus Henricsson

doi:10.1007/s00216-021-03372-x

Kelly Dimovska Nilsson, John S Fletcher + Show 3 more

Open Access

https://doi.org/10.1007/s00216-021-03372-x

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Journal: Analusis	Publication Date: May 11, 2021
Citations: 12	License type: open-access

Affiliation: University of Gothenburg, Uppsala University

Abstract

This work assesses the potential of new water cluster-based ion beams for improving the capabilities of secondary ion mass spectrometry (SIMS) for in situ lipidomics. The effect of water clusters was compared to carbon dioxide clusters, along with the effect of using pure water clusters compared to mixed water and carbon dioxide clusters. A signal increase was found when using pure water clusters. However, when analyzing cells, a more substantial signal increase was found in positive ion mode when the water clusters also contained carbon dioxide, suggesting that additional reactions are in play. The effects of using a water primary ion beam on a more complex sample were investigated by analyzing brain tissue from an Alzheimer’s disease transgenic mouse model. The results indicate that the ToF-SIMS results are approaching those from MALDI as ToF-SIMS was able to image lyso-phosphocholine (LPC) lipids, a lipid class that for a long time has eluded detection during SIMS analyses. Gangliosides, sulfatides, and cholesterol were also imaged.Graphical abstract

Highlights

Secondary ion mass spectrometry (SIMS) is one of the increasing number of imaging mass spectrometry approaches that combine the chemical specificity of mass spectrometry with imaging capabilities that in extreme cases can approach 10-nm lateral resolution [1,2,3]
We report the effects of different water clusters on lipid signals and that the use of cm2 for (H2O)18k+ (CO2) as a backing gas for the water cluster ion beam in some cases provides additional signal enhancement
Initial experiments were performed on commercially available lipid extract samples using water vapor with a N2 backing gas to ensure pure water cluster formation

Summary

Introduction

Secondary ion mass spectrometry (SIMS) is one of the increasing number of imaging mass spectrometry approaches that combine the chemical specificity of mass spectrometry with imaging capabilities that in extreme cases can approach 10-nm lateral resolution [1,2,3].Published in the topical collection Mass Spectrometry Imaging 2.0 with guest editors Shane R. Secondary ion mass spectrometry (SIMS) is one of the increasing number of imaging mass spectrometry approaches that combine the chemical specificity of mass spectrometry with imaging capabilities that in extreme cases can approach 10-nm lateral resolution [1,2,3]. Different imaging mass spectrometry approaches (e.g., MALDI or DESI) offer different advantages such as intact protein detection or ambient analysis [4, 5]. SIMS is unique in the ability to finely focus, and electrostatically scan, the ion beam used to probe the sample and deliver information with high surface sensitivity and high depth resolution, if the ion beam is used to gradually erode the sample during the analysis. Progress has been greatly aided by the development of a range of different ion beams that can be fired at the sample to generate the secondary ions that are extracted and analyzed in the mass spectrometer. High energy gold clusters (e.g., Au28008+) have been shown to enhance pseudo-molecular ion detection due to lower energy sputtering of secondary species [8]

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