Biocompatible Surface-Coated Probe for <i>in Vivo</i>, <i>in Situ</i>, and Microscale Lipidomics of Small Biological Organisms and Cells Using Mass Spectrometry

Lipidomics is a significant way to understand the structural and functional roles that lipids play in biological systems. Although many mass spectrometry (MS)-based lipidomics strategies have recently achieve remarkable results, <i>in vivo</i>, <i>in situ</i>, and microscale lipidomics for small biological organisms and cells have not yet been obtained. In this article, we report a novel lipidomics methodology for <i>in vivo</i>, <i>in situ</i>, and microscale investigation of small biological organisms and cells using biocompatible surface-coated probe nanoelectrospray ionization mass spectrometry (BSCP-nanoESI-MS). A novel biocompatible surface-coated solid-phase microextration (SPME) probe is prepared, which possesses a probe-end diameter of less than 5 μm and shows excellent enrichment capacity toward lipid species. <i>In vivo</i> extraction of living biological organisms (e.g., zebrafishes), <i>in situ</i> sampling a precise position of small organisms (e.g., <i>Daphnia magna</i>), and even microscale analysis of single eukaryotic cells (e.g., HepG2) are easily achieved by the SPME probe. After extraction, the loaded SPME probe is directly applied for nanoESI-MS analysis, and a high-resolution mass spectrometer is employed for recording spectra and identifying lipid species. Compared with the conventional direct infusion shotgun MS lipidomics, our proposed methodology shows a similar result of lipid profiles but with simpler sample pretreatment, less sample consumption, and shorter analytical times. Lipidomics of zebrafish, <i>Daphnia magna</i>, and HepG2 cell populations were investigated by our proposed BSCP-nanoESI-MS methodology, and abundant lipid compositions were detected and identified and biomarkers were obtained via multivariate statistical analysis