On-tissue Chemical Derivatizations for Untargeted Spatial Metabolomics

在化学系化学测量与成像项目和促进竞争性研究的既定项目（EPSCoR）的支持下，爱荷华州立大学的Young-Jin Lee教授和他的团队正在开发分析技术，以推进空间代谢组学。质谱成像（MSI）是一种流行的空间代谢组学工具，可以直接从组织中解剖不同细胞和细胞类型之间的代谢物差异。一个关键的瓶颈是有限的化合物覆盖由于低电离效率和小采样尺寸。为了克服这一限制，研究人员开始采用组织上化学衍生化（OTCD），但其应用仅限于选定代谢物的靶向成像。Lee小组正在探索OTCD- msi作为非靶向空间代谢组学的工具，通过将多个OTCD组合在顺序组织切片上，以增加总体代谢物覆盖率和注释置信度。潜在的影响跨越许多科学学科，包括药物发现，植物代谢组学，食品安全和生物医学科学，同时为学生提供令人兴奋的教育机会，从事生物和物理科学边界的跨学科研究。将通过各种渠道招募不同群体的学生参与该项目，包括通过美国化学会的project SEED招募高中生。在之前成功实现OTCD到METASPACE（一个免费的基于网络的空间代谢组学代谢物注释平台，由欧洲分子生物学实验室的Alexandrov小组主持）的基础上，这项研究将进一步推进非靶向空间代谢组学。首先，将开发生物信息学工具，通过使用功能群搜索算法来改进基于otcd的非靶向空间代谢组学中的代谢物注释。其次，将发展源内气相反应，以协助确定分子结构。脂质的碳-碳双键位置将使用臭氧气体来确定，而otcd衍生代谢物中不稳定氢的数量将使用重水蒸气来确定。最后，将研究微滴在OTCD中的加速反应，以更好地了解潜在的现象，并进一步提高OTCD的反应效率，特别是使用一种新的电喷雾电离（ESI）喷雾装置来研究电场的作用。结合基于metaspace的OTCD-MSI数据集分析，该方法有望帮助许多研究人员获得非靶向空间代谢组学。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

With support from the Chemical Measurement and Imaging Program in the Division of Chemistry and the Established Program to Stimulate Competitive Research (EPSCoR), Professor Young-Jin Lee and his group at Iowa State University are developing analytical technologies to advance spatial metabolomics. Mass spectrometry imaging (MSI) is a popular tool for spatial metabolomics to dissect metabolite differences between different cells and cell types directly from tissues. One critical bottleneck is limited compound coverage due to the low ionization efficiency and small sampling size. To overcome this limitation, researchers started to adopt on-tissue chemical derivatization (OTCD) but its application has been limited to targeted imaging of selected metabolites. The Lee group is exploring OTCD-MSI as a tool for untargeted spatial metabolomics by combining multiple OTCD on sequential tissue sections to increase overall metabolite coverage and annotation confidence. The potential impact spans across many scientific disciplines, including drug discovery, plant metabolomics, food safety, and biomedical science, while providing exciting educational opportunities for students to engage in interdisciplinary research at the boundary of biological and physical science. A diverse group of students will be recruited to participate in the project through various channels, including high school students through Project SEED of the American Chemical Society. Built upon previous success in implementing OTCD to METASPACE, a free web-based metabolite annotation platform for spatial metabolomics hosted by the Alexandrov group at the European Molecular Biology Laboratory, this research will further advance untargeted spatial metabolomics. First, bioinformatics tools will be developed to improve metabolite annotations in OTCD-based untargeted spatial metabolomics by using functional group search algorithms. Second, in-source gas-phase reactions will be developed to assist in determining molecular structures. Carbon-carbon double bond positions of lipids will be determined using ozone gas and the number of labile hydrogens in OTCD-derivatized metabolites using heavy water vapor. Finally, microdroplet reaction acceleration in OTCD will be investigated to better understand the underlying phenomena and further improve OTCD reaction efficiency, specifically regarding the role of the electric field using a new electrospray ionization (ESI) spray device. Combined with METASPACE-based analysis of OTCD-MSI datasets, this approach is expected to help make untargeted spatial metabolomics accessible to many researchers.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.