New Advances in Capillary Electrophoresis-Mass Spectrometry for Metabolomics: Multiplexed Separations for Biomarker Discovery

代谢组学是指对存在于生物体、细胞或生物标本（如血液）中的低分子量化合物（即代谢物）进行综合分析。由于代谢物是反映环境的基因表达的“现实世界”分子端点，非靶向代谢物谱分析（即代谢组学）为作出与人类健康有关的科学发现提供了一种有希望的方法，例如用于早期发现和治疗疾病的诊断性生物标志物。然而，由于“代谢组”的化学多样性和广泛的浓度范围，在复杂的生物样品中仍然很大程度上未被表征，因此需要新的分析策略。我们的实验室将利用最先进的毛细管电泳-质谱（CE-MS）技术为基础研究做出重要贡献，该技术解决了代谢组学的几个主要障碍，即样品通量低、灵敏度差和/或选择性有限。我们的提案将开发一种创新的代谢组学工作流程，用于基于多路分离的生物标志物发现，这将弥合样品吞吐量和数据保真度之间存在的主要差距。

Metabolomics refers to the comprehensive analysis of low molecular weight compounds (i.e., metabolites) that exist in an organism, cell or biological specimen, such as blood. Since metabolites act as "real-world" molecular endpoints of gene expression that reflect environment, untargeted metabolite profiling (i.e., metabolomics) offers a promising way to make scientific discoveries relevant to human health, such as diagnostic biomarkers for early detection and treatment of diseases. However, new analytical strategies are needed due to the chemical diversity and wide concentration range of "the metabolome" that remains largely uncharacterized in complex biological samples. Our laboratory will make important contributions to fundamental research using state-of-the-art capillary electrophoresis-mass spectrometry (CE-MS) technology that address several major obstacles in metabolomics, namely its low sample throughput, poor sensitivity and/or limited selectivity. Our proposal will develop an innovative metabolomics workflow for biomarker discovery based on multiplexed separations that will bridge the major gap existing between sample throughput and data fidelity. Sample throughput is limited when using conventional MS-based separation platforms due time requirements for solute elution and column pre-conditioning when analyzing "one sample at a time". Thus, major efforts are devoted to quality assurance and data pre-processing to correct for long-term instrumental drift that is time-consuming and subject to bias. To address these challenges, our research will develop multi-segment injection (MSI)-CE-MS based on serial injection of seven or more discrete sample segments "within a single capillary" as a way to increase sample throughput for large-scale metabolomic studies without added infrastructure or operating costs. This method offers an unprecedented strategy to encode information temporally with sample throughput analogous to direct infusion-ESI-MS (3 min/sample) while retaining all the benefits of a high efficiency separation. Our research will implement non-aqueous MSI-CE-MS in conjunction with chemoselective derivatization reactions to dramatically expand metabolome coverage with exquisite selectivity and sensitivity. Also, a multivariate model will be used to accurately predict ion migration and ionization responses for various classes of metabolites and their derivatives for unambiguous identification and quantification of unknown compounds of clinical relevance (e.g., biomarkers) in cases when authentic standards do not exist. Notably, an accelerated metabolomics workflow for biomarker discovery will be developed when using MSI-CE-MS in order to elucidate differential responses to lifestyle interventions that elicit positive health benefits for type 2 diabetes prevention, as well as diagnostic biomarkers that can be used to confirm the onset of stroke or provide better ways to test for cystic fibrosis. In all cases, customized injection sequences in MSI-CE-MS will be designed to reject spurious data and reduce false discoveries as a way to enhance data quality for translation of scientific discoveries into clinical practice. In summary, no other instrumental technique offers such a diverse array of analytical merits for metabolomics (e.g., high sample throughout, high data quality, low infrastructure costs) that will lead to new advances in clinical diagnostics and personalized medicine.