Müller Max A, Bhandari Dhaka R, Spengler Bernhard
Institute of Inorganic and Analytical Chemistry, Justus Liebig University, 35392 Giessen, Germany.
Metabolites. 2021 Sep 15;11(9):624. doi: 10.3390/metabo11090624.
Applications of mass spectrometry imaging (MSI), especially matrix-assisted laser desorption/ionization (MALDI) in the life sciences are becoming increasingly focused on single cell analysis. With the latest instrumental developments, pixel sizes in the micrometer range can be obtained, leading to challenges in matrix application, where imperfections or inhomogeneities in the matrix layer can lead to misinterpretation of MS images. Thereby, the application of premanufactured, homogeneous ionization-assisting devices is a promising approach. Tissue sections were investigated using a matrix-free imaging technique (Desorption Ionization Using Through-Hole Alumina Membrane, DIUTHAME) based on premanufactured nanostructured membranes to be deposited on top of a tissue section, in comparison to the spray-coating of an organic matrix in a MALDI MSI approach. Atmospheric pressure MALDI MSI ion sources were coupled to orbital trapping mass spectrometers. MS signals obtained by the different ionization techniques were annotated using accurate-mass-based database research. Compared to MALDI MSI, DIUTHAME MS images captivated with higher signal homogeneities, higher contrast and reduced background signals, while signal intensities were reduced by about one order of magnitude, independent of analyte class. DIUTHAME membranes, being applicable only on tissue sections thicker than 50 µm, were successfully used for mammal, insect and plant tissue with a high lateral resolution down to 5 µm.
质谱成像（MSI），尤其是基质辅助激光解吸/电离（MALDI）在生命科学中的应用越来越聚焦于单细胞分析。随着最新的仪器发展，可以获得微米范围内的像素尺寸，这给基质应用带来了挑战，因为基质层中的缺陷或不均匀性可能导致对MS图像的错误解读。因此，应用预制的、均匀的电离辅助装置是一种很有前景的方法。与在MALDI MSI方法中喷涂有机基质相比，使用基于预制纳米结构膜的无基质成像技术（使用通孔氧化铝膜的解吸电离，DIUTHAME）对组织切片进行了研究，该膜沉积在组织切片顶部。大气压MALDI MSI离子源与轨道阱质谱仪联用。通过基于精确质量的数据库研究对不同电离技术获得的MS信号进行注释。与MALDI MSI相比，DIUTHAME MS图像具有更高的信号均匀性、更高的对比度和更低的背景信号，而信号强度降低了约一个数量级，与分析物类别无关。DIUTHAME膜仅适用于厚度超过50 µm的组织切片，已成功用于哺乳动物、昆虫和植物组织，横向分辨率高达5 µm。
