Review of Recent Advances in Lipid Analysis of Biological Samples via Ambient Ionization Mass Spectrometry

The rapid and direct structural characterization of lipids proves to be critical for studying the functional roles of lipids in many biological processes. Among numerous analytical techniques, ambient ionization mass spectrometry (AIMS) allows for a direct molecular characterization of lipids from various complex biological samples with no/minimal sample pretreatment. Over the recent years, researchers have expanded the applications of the AIMS techniques to lipid structural elucidation via a combination with a series of derivatization strategies (e.g., the Paternò–Büchi (PB) reaction, ozone-induced dissociation (OzID), and epoxidation reaction), including carbon–carbon double bond (C=C) locations and sn-positions isomers. Herein, this review summarizes the reaction mechanisms of various derivatization strategies for C=C bond analysis, typical instrumental setup, and applications of AIMS in the structural elucidation of lipids from various biological samples (e.g., tissues, cells, and biofluids). In addition, future directions of AIMS for lipid structural elucidation are discussed.

Automated High-Throughput System Combining Small-Scale Synthesis with Bioassays and Reaction Screening

The Purdue Make It system is a unique automated platform capable of small-scale in situ synthesis, screening small-molecule reactions, and performing direct label-free bioassays. The platform is based on desorption electrospray ionization (DESI), an ambient ionization method that allows for minimal sample workup and is capable of accelerating reactions in secondary droplets, thus conferring unique advantages compared with other high-throughput screening technologies. By combining DESI with liquid handling robotics, the system achieves throughputs of more than 1 sample/s, handling up to 6144 samples in a single run. As little as 100 fmol/spot of analyte is required to perform both initial analysis by mass spectrometry (MS) and further MSn structural characterization. The data obtained are processed using custom software so that results are easily visualized as interactive heatmaps of reaction plates based on the peak intensities of m/ z values of interest. In this paper, we review the system’s capabilities as described in previous publications and demonstrate its utilization in two new high-throughput campaigns: (1) the screening of 188 unique combinatorial reactions (24 reaction types, 188 unique reaction mixtures) to determine reactivity trends and (2) label-free studies of the nicotinamide N-methyltransferase enzyme directly from the bioassay buffer. The system’s versatility holds promise for several future directions, including the collection of secondary droplets containing the products from successful reaction screening measurements, the development of machine learning algorithms using data collected from compound library screening, and the adaption of a variety of relevant bioassays to high-throughput MS.

A Template for the Validation of DART-MS for Qualitative Seized Drugs Analysis

Direct analysis in real time mass spectrometry (DART-MS) is an increasingly employed tool for a wide range of forensic applications including seized drug analysis. A significant body of research surrounds DART-MS for the analysis of seized drugs and how it can be used to address many of the challenges caused by the increased presence of emerging drugs and novel psychoactive substances. A lack of available resources to help address validation, operation, training, and data interpretation needs is just one of the hurdles that laboratories face when adopting new technologies, such as DART-MS. To provide additional resources to assist in validation development, this work provides a template that can be adopted or adapted for DART-MS or other ambient ionization mass spectrometry techniques for qualitative seized drug analysis. The template, which was created as a result of recent implementation efforts, provides a description of validation studies with a focus on understanding the potential challenges and limitations caused by the prevalence of novel psychoactive substances and other emerging drugs. The studies address accuracy and precision, reproducibility, specificity, sensitivity, environmental factors, use in casework, and robustness. In addition to providing a template for validation, the results obtained from completing these studies on two high-resolution DART-MS systems are also presented. This work, and the corresponding supplemental information, was created to add to the available resources that laboratories can leverage to assist in overcoming the adoption hurdles of ambient ionization mass spectrometry methods such as DART-MS.

Mass spectrometry based high-throughput bioanalysis of low molecular weight compounds: are we ready to support personalized medicine?

Liquid chromatography coupled to mass spectrometry (LC-MS) is the gold standard in bioanalysis for the development of quantitative assays to support drug development or therapeutic drug monitoring. High-throughput and low-cost gene sequencing have enabled a paradigm shift from one treatment fits all to personalized medicine (PM). However, gene monitoring provides only partial information about the health state. The full picture requires the combination of gene monitoring with the screening of exogenous compounds, metabolites, lipids, and proteins. This critical review discusses how mass spectrometry–based technologies and approaches including separation sciences, ambient ionization, and ion mobility are/could be used to support high-throughput bioanalysis of endogenous end exogenous low molecular weight compounds. It includes also various biological sample types (from blood to expired air), and various sample preparation techniques. Graphical abstract