Capillary Electrophoresis with Electrospray Ionization Mass Spectrometric Detection for Single-Cell Metabolomics

Abstract

A method that enables metabolomic profiling of single cells and subcellular structures is described using capillary electrophoresis coupled to electrospray ionization time-of-flight mass spectrometry. A nebulizer-free coaxial sheath-flow interface completes the circuit and provides a stable electrospray, yielding a signal with a relative standard deviation of under 5% for the total ion electropherogram. Detection limits are in the low nanomolar range (i.e., < 50 nM (< 300 amol)) for a number of cell-to-cell signaling molecules, including acetylcholine (ACh), histamine, dopamine, and serotonin. The instrument also yields high efficiency separations, e.g., ~600,000 for eluting ACh bands. The utility of this setup for single cell metabolomic profiling is demonstrated with identified neurons from Aplysia californica-the R2 neuron and metacerebral cell (MCC). Single cell electropherograms are reproducible, with a large number of metabolites detected; more than 100 compounds yield signals of over 10 4 counts from the injection of only 0.1% of the total content from a single MCC. Expected neurotransmitters are detected within the cells (ACh in R2 and serotonin in MCC), as are compounds that have molecular masses consistent with all of the naturally-occurring amino acids (except cysteine). Tandem MS using a quadrupole time-of-flight tandem mass spectrometer distinguishes ACh from isobaric compounds in the R2 neuron and demonstrates the ability of this method to characterize and identify metabolites present within single cells.

Analytical techniques for single-cell metabolomics: state of the art and trends

“…Along these lines, an interesting approach to single-cell metabolomics was demonstrated by the group of Sweedler [75]. Low molecular weight compounds were analyzed in single neurons of Aplysia californica by CE coupled with nanoESI-MS (Fig.…”

Small-Volume Analysis of Cell–Cell Signaling Molecules in the Brain

“…CE-MS (see Figure 3a) is widely used to measure and identify bioactive peptides (Ye et al, 2011), metabolites (Nemes et al, 2011(Nemes et al, , 2012Nautiyal et al, 2012;Gholipour et al, 2013), classical neurotransmitters (Lapainis et al, 2009), and amino acids (Moini, 2013). Alternatively, microdialysis sampling can be directly coupled to ESI-MS via nanodroplet segmented flow for in vivo chemical monitoring of neurotransmitters, metabolites, and drugs in the live brain (Song et al, 2012).…”

MS‐based analytical methodologies to characterize genetically modified crops

“…Thus, around 1,700 different metabolites were detected (of which 150 were identified) with CE-MS from bacteria-cell extracts with two different methods and scanning from m/z 70 to 1,027 in intervals of 30 Th (Soga et al, 2003). Moreover, in a recent article, single cells and subcellular metabolomes could also be investigated with CE-MS (Lapainis, Rubakhin, & Sweedler, 2009). Some attempts have been made to carry out metabolome analysis in higher plants with CE-MS methods (Sato et al, 2004;Edwards et al, 2006;Harada et al, 2008).…”