Imaging mass spectrometry for in situ lipidomics: from cell structures to cardiac tissue
Doktorsavhandling, 2018

Imaging of cells and tissues is important for studying different processes within biological systems due to the spatial information provided for different molecular species during imaging. One powerful imaging technique is mass spectrometry imaging (MSI). It is a label free technique that provides chemical information of a sample at the same time as it allows for imaging at high spatial resolution. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) uses a focused primary ion beam to ablate and ionise molecules from the top layers of the sample surface which makes it a very surface sensitive technique. Recent developments in high energy gas cluster ion beam (GCIB) technology for ToF-SIMS has greatly improved the imaging of higher mass species, such as intact lipids. Lipids are important molecules found in all living organisms. They are used as building blocks for cells and are involved in a variety of important cellular processes such as energy storage and acting as important mediators in many signalling pathways, making them an interesting target for imaging studies. In this thesis, the ToF-SIMS imaging technique has been applied to both tissues and cells in order to perform in situ lipidomics analysis of various samples. Development of sample treatment methods that provides easier data interpretation and other method development for improving secondary ion yields have also been implemented in this work. In paper I, enhancement of negative secondary ion yields was induced by a combination of ion bombardment using a GCIB with simultaneous caesium flooding, for both inorganic and organic substrates. In paper II, ToF-SIMS imaging with a GCIB was used together with LC-MS to elucidate changes in lipid composition 6 hours after an induced myocardial infarction in mouse heart. The spatial information from the MSI allowed correlation of specific lipid species to infarcted and non-infarcted regions of the heart. Localised lipid accumulation was discovered in specific regions of the heart. In paper IV, these lipid changes were tracked over longer periods of time, 24 hours and 48 hours after infarction, and progression of the infarcted area was observed. In paper III, a simple method was developed in order to aid interpretation of the complex mass spectra collected from ToF-SIMS experiments of complex tissue sample such as heart tissue. Salt adduct formation was demonstrated as a means to discriminate between diacylglyceride and triacylglyceride, which are usually impossible to distinguish during ToF-SIMS analysis. In paper V, lipid changes in PC12 cell membranes were analysed after incubation with the essential fatty acids, omega-3 and omega-6. Using deuterium labelled fatty acids made it possible to track incorporation into phospholipids as well as the relative amount of each.

Myocardial infarction

PC12 cells

Cell membrane

Mass spectrometry imaging

Sample preparation

Lipidomics

ToF-SIMS

Gas cluster ion beam

KB-salen, Kemigården 4.
Opponent: Dr. Alex Shard, Analytical Sciences Division, National Physics Laboratory, UK

Författare

Sanna Sämfors

Chalmers, Kemi och kemiteknik, Kemi och biokemi, Analytisk kemi

Significant Enhancement of Negative Secondary Ion Yields by Cluster Ion Bombardment Combined with Cesium Flooding

Analytical Chemistry,; Vol. 87(2015)p. 10025-10032

Artikel i vetenskaplig tidskrift

Localised Lipid Accumulation Detected in Infarcted Mouse Heart Tissue using ToF-SIMS

International Journal of Mass Spectrometry,; (2017)

Artikel i vetenskaplig tidskrift

Sanna Sämfors, Andrew G. Ewing, John S. Fletcher, Salt adduct formation for the discrimination of diacylglyceride and triacylglyceride ions in ToF-SIMS analysis

Sanna Sämfors, Jan Borén, John S. Fletcher, Spatio-temporal changes in lipid composition in infarcted mouse heart tissue elucidated by ToF-SIMS imaging

Mai H. Philipsen, Sanna Sämfors, Per Malmberg, Andrew G. Ewing, Relative quantification of deuterated Omega-3 and -6 fatty acids and their lipid turnover in PC12 cell membraned using ToF-SIMS

Lipider är en grupp molekyler som finns i alla levande organismer. De kan användas som byggstenar för celler, som är den minsta funktionella biologiska enheten i en levande organism. Celler använder inte endast lipiderna som byggstenar, de kan också användas i många andra viktiga processer i en cell som exempelvis energiförvaringsmolekyler och som ett kommunikationsredskap. Förändringar i lipidmängd eller lipidsammansättning har i tidigare forskning visat sig spela en roll i många sjukdomsprocesser, vilket gör lipider till viktiga molekylar att studera i arbetet för förebyggandet av sjukdomar. En avbildningsmetod, kallad mass-spektrometriavbildning, har visat sig användbar för att studera lipidsammansättning i olika biologiska system. Avbildningstekniken kombinerar möjligheten att samtidigt som man skapar högupplösta bilder så samlar man in kemisk information om proverna. Detta gör att det med mass-spektrometriavbildning är möjligt att skapa kemiska kartor av det analyserade provet som visar lipidmolekylernas olika positioner på ytan av provet. Informationen som erbjuds av analysen kan vara användbar för att skapa bättre förståelse om de kemiska processer som pågår i det analyserade provet. I min avhandling har den här avbildningstekniken använts för att studera förändringar i lipidsammansättning när det kommer till hjärtvävnad från ett hjärta som genomgått en hjärtinfarkt. Målet har varit att förstå vilka lipidförändringar som sker vid en infarkt och hur detta bryter ner vävnaden. Lipidförändringarna kan vara potentiella mål för utveckling av nya läkemedel, vilket gör att arbetet kan leda till bättre behandlingsmetoder för patienter som drabbats av hjärtinfarkt.

Ämneskategorier

Biokemi och molekylärbiologi

Analytisk kemi

Kemi

Infrastruktur

Infrastruktur för kemisk avbildning

ISBN

978-91-7597-729-4

Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4410

Utgivare

Chalmers tekniska högskola

KB-salen, Kemigården 4.

Opponent: Dr. Alex Shard, Analytical Sciences Division, National Physics Laboratory, UK

Mer information

Senast uppdaterat

2018-04-27