FTMS Laboratory for Human Health Research, Department of Chemistry, North Carolina State University, Raleigh, North Carolina, USA.
Rapid Commun Mass Spectrom. 2023 Nov 30;37(22):e9638. doi: 10.1002/rcm.9638.
Infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI) utilizes a 2970 nm mid-IR laser to desorb samples with depth resolutions (Z) on the order of micrometers. Conventionally, 5-20 μm thick tissue sections are used to characterize different applications of the IR-MALDESI source, but an optimal thickness has not been systematically investigated.
Mouse liver was sectioned to various thicknesses and analyzed using IR-MALDESI mass spectrometry imaging (MSI). Height profiles of tissue sections of various cryosectioned thicknesses were acquired to affirm tissue thickness. Tissue sections of each thickness were measured using a Keyence microscope. Paraffin wax was cryosectioned, mounted on microscope slides, and measured using a chromatic confocal sensor system to determine the cryostat sectioning accuracy.
Analyzing sectioned tissues at higher thickness (>10 μm) leads to lower ion abundance, a decrease in signal over long analysis times, and more frequent instrument cleaning. Additionally, increasing tissue thickness above the optimum (7 μm) does not result in a significant increase in lipid annotations.
This work defines an optimal sample thickness for IR-MALDESI-MSI and demonstrates the utility of optimizing tissue thickness for MSI platforms of comparable Z resolution.
红外矩阵辅助激光解吸电喷雾电离（IR-MALDESI）利用 2970nm 中红外激光对深度分辨率（Z）在微米量级的样品进行解吸。传统上，使用 5-20μm 厚的组织切片来表征 IR-MALDESI 源的不同应用，但尚未系统地研究最佳厚度。
将小鼠肝脏切成不同厚度，并使用红外 MALDESI 质谱成像（MSI）进行分析。获取不同冷冻切片厚度的组织切片高度轮廓，以确认组织厚度。使用 Keyence 显微镜测量各厚度的组织切片。将石蜡包埋组织冷冻切片，安装在显微镜载玻片上，并使用彩色共聚焦传感器系统进行测量，以确定冷冻切片机的切片精度。
分析较厚（>10μm）的切片组织会导致离子丰度降低、长时间分析信号衰减以及更频繁的仪器清洗。此外，增加组织厚度超过最佳厚度（7μm）并不会导致脂质注释显著增加。
这项工作定义了 IR-MALDESI-MSI 的最佳样品厚度，并展示了优化组织厚度对于具有类似 Z 分辨率的 MSI 平台的实用性。
