Single Cell Untargeted Lipidomics Using Liquid Chromatography Ion Mobility-Mass Spectrometry

Advancements in technology over the years have propelled omics analysis to the level of single cell resolution. Following the breakthroughs in single cell transcriptomics and genomics, single cell proteomics has recently rapidly progressed, aided by highly sensitive mass spectrometry instrumentation. However, there is currently a paucity of studies and methodologies for single cell lipidomics, aside from imaging-based approaches. Profiling lipids at the single cell level holds promise for providing novel insights into the complex heterogeneity of cells in various human disorders. Further, by integrating single cell lipidomics with other single cell omics including proteomics, it becomes possible to achieve single cell multiomics, enabling the discovery of novel molecular signatures. We developed untargeted single cell lipidomics using nanoflow liquid chromatography-ion mobility spectrometry-mass spectrometry. To enhance lipid coverage at the single cell level, the method was conducted in both positive and negative ion modes. We identified an average of 161 lipids spanning phospholipids, sphingolipids, cholesteryl esters, and glycerides in positive ion mode from single cells of human cholangiocarcinoma cells based on a rule-based lipid annotation. Additionally, an average of 20 species of phospholipids was identified in the negative ion mode. These preliminary data demonstrate a new methodology to profile lipids at a single or low input of cells.