Capillary flow-based sample preparation system for metabolomic analysis of mammalian cells in suspension

Sample preparation methodology is critical to obtaining reliable data for studying endogenous metabolites. Dependable preparation techniques require separation of cells from culture media, quenching of enzymatic activity, and extraction of metabolites from the cells. Presented here is a simple, rapid, semi-automated metabolomic sample preparation technique for 20 μL samples of RAW 264.7 cells suspended in culture media. This method uses online filter-assisted electroporation-based cell lysis and chilled organic solvent extraction to prepare metabolomic samples from cells in suspension in 2 min. Experiments using an isotopically labeled adenosine triphosphate internal standard were carried out to ensure enzymatic quenching by monitoring the ratio of labeled adenosine diphosphate to adenosine triphosphate. Cells were metabolically labeled with ¹³C-glucose concurrent with sampling aliquots of the cell suspension over the course of 24 h. Incorporation of ¹³C into organic acid metabolites such as itaconate Cell lysates was analyzed by nano-reverse-phase liquid chromatography-mass spectrometry (nano-RP-LC-MS), showing incorporation of ¹³C into organic acid metabolites such as itaconate.