Hybrid Ionization Source Combining Nanoelectrospray and Dielectric Barrier Discharge Ionization for the Simultaneous Detection of Polar and Nonpolar Compounds in Single Cells

Abstract

Single-cell metabolomics is expected to deliver fast and dynamic information on cell function; therefore, it requires rapid analysis of a wide variety of very small quantities of metabolites in living cells. In this work, a hybrid ionization source that combines nanoelectrospray ionization (nanoESI) and dielectric barrier discharge ionization (DBDI) is proposed for single-cell analysis. A capillary with a 1 μm i.d. tip was inserted into cells for sampling and then directly used as the nanoESI source for ionization of polar metabolites. In addition, a DBDI source was employed as a post-ionization source to improve the ionization of apolar metabolites in cells that are not easily ionized by ESI. By increasing the voltage of the DBDI source from 0 to 3.2 kV, the classes of detected metabolites can be shifted from mostly polar to both polar and apolar to mainly apolar. Plant cells (onion) and human cells (PANC-1) were investigated in this study. After optimization, 50 compounds in onion cells and 40 compounds in PANC-1 cells were observed in ESI mode (3.5 kV) and an additional 49 compounds in onion cells and 73 compounds in PANC-1 cells were detected in ESI (3.5 kV)-DBDI (2.6 kV) hybrid mode. This hybrid ionization source improves the coverage, ionization efficiency, and limit of detection of metabolites with different polarities and could potentially contribute to the fast-growing field of single-cell metabolomics.

High-throughput analysis of anthocyanins in horticultural crops using probe electrospray ionization tandem mass spectrometry (PESI/MS/MS)

“…In strawberries, the differences observed between achene and receptacle would provide insights to accelerate the elucidation of the physiological mechanism and breeding of new cultivars with independent colors in these organs [ 44 ]. A combinatorial approach using microscopy and probes may help elucidate mechanisms underlying the differences in metabolite accumulation at the cellular level [ 15 ].…”

Development of a 3D-Printed Ionization Source for Single-Cell Analysis

“…In recent years, mass spectrometry has been widely used for single-cell metabolomic analyses because it is very sensitive and highly specific and able to analyze multiple molecules simultaneously. − The electrospray ionization (ESI) source is one of the most popular used ionization sources in single-cell mass spectrometry. ,− ,, It is an atmospheric pressure ionization source that does not require a vacuum operating environment and can sample single cells in situ for analysis. For example, Masujima and colleagues pioneered this field by developing a “live single-cell MS” (live MS) method and using it to investigate subcellular metabolites in RBL-2H3 (rat leukemia cell line), plant cells, , and CTCs .…”

“…4 In recent years, mass spectrometry has been widely used for single-cell metabolomic analyses because it is very sensitive, highly specific, and able to analyze multiple molecules simultaneously. [5][6][7][8][9][10][11][12][13][14][15][16][17] The electrospray ionization (ESI) source is one of the most popular used ionization sources in single-cell mass spectrometry. 7,[10][11][12]14,17 It is an atmospheric pressure ionization source that does not require a vacuum operating environment and can sample single cells in situ for analysis.…”

Flexible Microtube Plasma for the Consecutive-Ionization of Cholesterol in Nano-Electrospray Mass Spectrometry

“…The Zenobi group combined an offline operated nano-ESI (nESI) with a DBDI source for the analysis of single cells and showed a stepwise increased ionization efficiency of small, less-polar metabolites. 28 In 2018, a comparison of three MS scan methods on a highly modern Orbitrap Fusion Tribrid mass spectrometer to determine cholesterol concentrations was published. 29 In this study, the best results are given by the multiplexed MS/MS (MSX) technique followed by parallel reaction monitoring (PRM), and high-resolution Fourier Transform MS (FTMS) in full-scan acquisition.…”

“…Furthermore, some publications deal with dual ionization sources of ESI and APCI, but antagonistic ionization conditions (e.g., temperature) or the dependencies of the power supplies of both sources make it difficult to switch between these sources within seconds. , This makes it unsuitable for liquid chromatographic separations within one measurement. The Zenobi group combined an offline operated nano-ESI (nESI) with a DBDI source for the analysis of single cells and showed a stepwise increased ionization efficiency of small, less-polar metabolites …”