Mass spectrometry-based characterization of endogenous peptides and metabolites in small volume samples

Abstract

Technologies to assay single cells and their extracellular microenvironments are valuable in elucidating biological function, but there are challenges. Sample volumes are low, the physicochemical parameters of the analytes vary widely, and the cellular environment is chemically complex. In addition, the inherent difficulty of isolating individual cells and handling small volume samples complicates many experimental protocols. Here we highlight a number of mass spectrometry (MS)-based measurement approaches for characterizing the chemical content of small volume analytes, with a focus on methods used to detect intracellular and extracellular metabolites and peptides from samples as small as individual cells. MS has become one of the most effective means for analyzing small biological samples due to its high sensitivity, low analyte consumption, compatibility with a wide array of sampling approaches, and ability to detect a large number of analytes with different properties without preselection. Having access to a flexible portfolio of MS-based methods allows quantitative, qualitative, untargeted, targeted, multiplexed, spatially resolved investigations of single cells and their similarly scaled extracellular environments. Combining MS with on-line and off-line sample conditioning tools, such as microfluidic and capillary electrophoresis systems, significantly increases the analytical coverage of the sample’s metabolome and peptidome, and improves individual analyte characterization / identification. Small volume assays help to reveal the causes and manifestations of biological and pathological variability, as well as the functional heterogeneity of individual cells within their microenvironments and within cellular populations.

Single Cell Profiling Using Ionic Liquid Matrix-Enhanced Secondary Ion Mass Spectrometry for Neuronal Cell Type Differentiation

“…Thus, a successful single cell analytical technique should provide a low absolute detection limit, a high dynamic range, and multiplexed coverage of analyte classes. 5 Mass spectrometry (MS) has become a versatile and robust method for performing volume-limited biological measurements. Mass spectrometry imaging (MSI) is at the forefront of MS-based, label-free platforms for analyzing single cells, 6,14-18 demonstrating cellular and subcellular spatial resolution 19-21 and untargeted detection of biological molecules.…”

Monitoring cell secretions on microfluidic chips using solid-phase extraction with mass spectrometry

“…Several studies have reported integration of on-line analysis of perfusates to monitor cellular secretions on chips [21, 22]. Immunoassay [23–25] or enzyme assay [26–28] with fluorescent detection, capillary electrophoresis with electrochemical detection [29], and enzyme assay with chemiluminescent detection [30] have all been used.…”

Using Dicationic Ion-Pairing Compounds To Enhance the Single Cell Mass Spectrometry Analysis Using the Single-Probe: A Microscale Sampling and Ionization Device

“…Traditional MS approaches to cell analysis were restricted to a population of cells (such as cell lysate), where an averaged result is obtained. Recent advancements in high mass resolution MS has allowed for the confident assignment of large numbers of molecules, 15 and improved sensitivity enables MS to be applied at the single cell level, mostly in the field of metabolomics, 14 and potentially single cell peptidomics 16 and proteomics. 17 Current SCMS techniques can be broadly categorized into nonambient and ambient techniques, based on their sampling environment.…”