Abstract
Metabolomics studies using a small amount of cells may save time and money, while in some cases (e.g., profiling pathogenic cells in an early-stage tissue), only a small number of cells are accessible for analysis. The analysis of small amounts of biological samples challenges the analytical toolbox used in present-day metabolomics studies, and a significant number of crucial biological questions cannot be properly addressed. To allow metabolic profiling of limited sample amounts, the potential of capillary electrophoresis-mass spectrometry (CE–MS) using a sheathless porous tip interface has been assessed using HepG2 cells in starting amounts of 500 and 10,000 cells as a model system in this work. It is shown that highly efficient and information-rich metabolic profiles for cationic metabolites at low-pH separation conditions could be obtained by sheathless CE–MS using an injection volume of only circa 42 nL, which equals the content/aliquot of circa 0.25 and 5 HepG2 cells, respectively. With as little as the content of 0.25 cell injected, more than 24 cationic metabolites could be identified. A further improvement of sample preparation and/or the injection part is required in order to effectively analyze the compounds of interest in very low sample amounts by sheathless CE–MS. However, the results obtained so far clearly indicate the strong potential of the proposed method for metabolic profiling of limited sample amounts.
Highlights
The final aim of a metabolomics study is to find an answer to a given biological or clinical question [1]
The conventional analytical techniques can be used in a reliable way for metabolomics studies, these analytical tools are often not suited for the profiling of metabolites in small amounts of biological samples
We have considered a sheathless capillary electrophoresis-mass spectrometry (CE–MS) approach, which was originally developed by Moini [12], for metabolic profiling of limited amounts of cells, as this
Summary
The final aim of a metabolomics study is to find an answer to a given (well-defined) biological or clinical question [1] For this purpose, advanced analytical separation techniques are used for targeted or nontargeted analysis of (endogenous) metabolites in biological samples to determine the influence of genetic variation or external stimuli [2]. For researches focused on stem cells [6], circulating tumor cells in blood [7], cancer stem cells, and primary tumor cells in early-stage tissues [8,9], often only a small amount of cells are available Another type of biomass-limited samples come from the emerging microfluidic 3D cell models, which can simulate physiological tissues by arranging different cell types in a 3D environment within a proper micro-environment [10]. These microfluidic cell culture systems intrinsically deal with relatively low amount of cell numbers, i.e. typically in the range of hundreds to thousands of cells
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