Abstract：
Mass spectrometry imaging (MSI) has become a significant tool for measuring chemical species in biological tissues, where much of the impact of these platforms lies in their capability to report the spatial distribution of analytes for correlation to sample morphology. As a result, enhancement of spatial resolution has become a frontier of innovation in the field, and necessary developments are dependent on the ionization source. More particularly, laser-based imaging sources may require modifications to the optical train or alternative sampling techniques. These challenges are heightened for systems with infrared (IR) lasers, as their operating wavelength generates spot sizes that are inherently larger than their ultraviolet counterparts. Recently, the infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI) source has shown the utility of a diffractive optical element (DOE) to produce square ablation patterns, termed top-hat IR-MALDESI. If the DOE optic is combined with oversampling methods, smaller ablation volumes can be sampled to render higher spatial resolution imaging experiments. Further, this approach enables reproducible spot sizes and ablation volumes for better comparison between scans. Herein, we investigate the utility of oversampling with top-hat IR-MALDESI to enhance the spatial resolution of measured lipids localized within the head of sectioned zebrafish tissue. Four different spatial resolutions were evaluated for data quality (e.g., mass measurement accuracy, spectral accuracy) and quantity of annotations. Other experimental parameters to consider for high spatial resolution imaging are also discussed. Ultimately, 20 μm spatial resolution was achieved in this work and supports feasibility for use in future IR-MALDESI studies.
摘要：
质谱成像（MSI）已成为测量生物组织中化学物质的重要工具。这些平台的大部分影响在于它们能够报告分析物的空间分布以与样品形态相关。因此,提高空间分辨率已成为该领域创新的前沿,和必要的发展取决于电离源。更具体地说,基于激光的成像源可能需要修改光学系统或替代采样技术。对于具有红外（IR）激光器的系统，这些挑战更加突出。因为它们的工作波长产生的光斑尺寸固有地大于它们的紫外线对应物。最近,红外矩阵辅助激光解吸电喷雾电离（IR-MALDESI）源已显示出衍射光学元件（DOE）产生正方形烧蚀图案的实用性，称为顶帽IR-MALDESI。如果DOE光学元件与过采样方法相结合，可以对较小的消融体积进行采样以呈现较高的空间分辨率成像实验。Further,这种方法能够实现可重复的斑点大小和消融体积,以便更好地比较扫描.在这里，我们研究了使用顶帽IR-MALDESI进行过采样以增强位于斑马鱼组织头部内的测量脂质的空间分辨率的实用性。评估了四种不同的空间分辨率的数据质量(例如，质量测量精度,光谱精度)和注释数量。还讨论了用于高空间分辨率成像的其他实验参数。最终,在这项工作中实现了20μm的空间分辨率，并支持在未来的IR-MALDESI研究中使用的可行性。
