Metal Oxide Laser Ionization Mass Spectrometry Imaging of Fatty Acids and Their Double Bond Positional Isomers,Analytical Chemistry

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Metal Oxide Laser Ionization Mass Spectrometry Imaging of Fatty Acids and Their Double Bond Positional Isomers
Analytical Chemistry ( IF 6.7 ) Pub Date : 2022-06-17 , DOI: 10.1021/acs.analchem.2c00551
Monika Koktavá ₁ , Jan Valášek ₁ , Dominika Bezdeková ₁ , Vadym Prysiazhnyi ₁ , Barbora Adamová ₂ , Petr Beneš _{2,

3} , Jarmila Navrátilová _{2,

3} , Michal Hendrych ₄ , Petr Vlček ₅ , Jan Preisler ₁ , Antonín Bednařík ₁

Affiliation

We present a novel combination of a metal oxide laser ionization mass spectrometry imaging (MOLI MSI) technique with off-line lipid derivatization by ozone for the detection of fatty acids (FA) and their carbon–carbon double bond (C═C) positional isomers in biological tissues. MOLI MSI experiments were realized with CeO₂ and TiO₂ nanopowders using a vacuum matrix-assisted laser desorption/ionization time-of-flight (MALDI TOF) mass spectrometer in the negative mode. The catalytic properties of these metal oxides allow FA cleavage from phospholipids under UV laser irradiation. At the same time, fragile ozonides produced at the sites of unsaturation decomposed, yielding four diagnostic ions specific for the C═C positions. Advantageously, two MOLI MSI runs from a single tissue sprayed with the metal oxide suspension were performed. The first run prior to ozone derivatization revealed the distribution of FAs, while the second run after the reaction with ozone offered additional information about FA C═C isomers. The developed procedure was demonstrated on MSI of a normal mouse brain and human colorectal cancer tissues uncovering the differential distribution of FAs down to the isomer level. Compared to the histological analysis, MOLI MSI showed the distinct distribution of specific FAs in different functional parts of the brain and in healthy and cancer tissues pointing toward its biological relevance. The developed technique can be directly adopted by laboratories with MALDI TOF analyzers and help in the understanding of the local FA metabolism in tissues.

中文翻译：

脂肪酸及其双键位置异构体的金属氧化物激光电离质谱成像

我们提出了一种将金属氧化物激光电离质谱成像 (MOLI MSI) 技术与通过臭氧进行离线脂质衍生化的新组合，用于检测脂肪酸 (FA) 及其碳-碳双键 (C=C) 位置异构体在生物组织中。MOLI MSI 实验是用 CeO ₂和 TiO _2实现的使用真空基质辅助激光解吸/电离飞行时间（MALDI TOF）质谱仪在负模式下制备纳米粉末。这些金属氧化物的催化特性允许在紫外激光照射下从磷脂中裂解 FA。同时，在不饱和位置产生的易碎臭氧化物分解，产生四种对 C=C 位置特异的诊断离子。有利地，从用金属氧化物悬浮液喷涂的单个组织进行两次MOLI MSI运行。臭氧衍生前的第一次运行揭示了 FA 的分布，而与臭氧反应后的第二次运行提供了有关 FA C=C 异构体的更多信息。开发的程序在正常小鼠大脑和人类结肠直肠癌组织的 MSI 上得到证实，揭示了 FA 的差异分布，直至异构体水平。与组织学分析相比，MOLI MSI 显示特定 FA 在大脑不同功能部位以及健康和癌症组织中的明显分布，表明其生物学相关性。所开发的技术可以直接被具有 MALDI TOF 分析仪的实验室采用，并有助于了解组织中的局部 FA 代谢。

更新日期：2022-06-17

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