Infrared Matrix-Assisted Laser Desorption Electrospray Ionization (IR-MALDESI) Imaging Source Coupled to a FT-ICR Mass Spectrometer

Abstract

Mass spectrometry imaging (MSI) allows for the direct monitoring of the abundance and spatial distribution of chemical compounds over the surface of a tissue sample. This technology has opened the field of mass spectrometry to numerous innovative applications over the past 15 years. First used with SIMS and MALDI MS that operate under vacuum, interest has grown for mass spectrometry ionization sources that allow for effective imaging but where the analysis can be performed at ambient pressure with minimal or no sample preparation. We introduce here a versatile source for MALDESI imaging analysis coupled to a hybrid LTQ-FT-ICR mass spectrometer. The imaging source offers single shot or multi-shot capability per pixel with full control over the laser repetition rate and mass spectrometer scanning cycle. Scanning rates can be as fast as 1 pixel/second and a spatial resolution of 45 μm was achieved with oversampling.

Mass Spectrometry Imaging Reveals Heterogeneous Efavirenz Distribution within Putative HIV Reservoirs

“…This attribute is an important advantage for the combinatorial nature of HAART and has already led to the implementation of MSI in the drug development process (7). One approach to MSI that is particularly well suited to the analysis of small molecules is infrared matrix-assisted laser desorptionelectrospray ionization (IR-MALDESI) (8), which allows the detection of ARVs in human tissue, as we have previously demonstrated (9,10).…”

Direct Analysis of Triterpenes from High-Salt Fermented Cucumbers Using Infrared Matrix-Assisted Laser Desorption Electrospray Ionization (IR-MALDESI)

“…The energy of the laser pulse is absorbed by the endogenous water present in the sample with the optional addition of ice as an external matrix. The method has in this specific application been abbreviated as IR-MALDESI [18]. In our laboratory, the instrument is routinely used for mass spectrometry imaging (MSI) of biological tissues without desalting or other chemical processing, and has proven to be useful for analyzing the spatial distributions of metabolites and drugs in tissue specimens [19,20].…”

Ambient Molecular Analysis of Biological Tissue Using Low-Energy, Femtosecond Laser Vaporization and Nanospray Postionization Mass Spectrometry

“…Molecular profiling and imaging of animal tissue samples with minimal sample preparation have been demonstrated by several ambient ionization MS techniques, including DESI [9,25,61], nano-DESI [10,22], IR-MALDESI [11,62], and LAESI [12,63]. To investigate the possibility of using LEMS for the analysis of animal samples, mouse brain was chosen in our analysis.…”

“…This suggests that sample preparation is important to avoid ion suppression in the LEMS analysis of animal tissue samples. The OCT compound embedding process should be avoided; rather, flash freezing of the tissue block followed by cryosectioning to produce thin slices that are amenable to ambient ionization MS analysis [11,12].…”

“…The goal of understanding complex biological systems, ranging from intact body [7] to tissue sections [8][9][10][11][12], to body fluids [13,14], to single cells [15,16], has been the driving force for the advent of various ambient ionization MS techniques in the last decade. Plasma-based techniques like direct analysis in real time (DART) or low temperature plasma (LTP) are ideal for the analysis of volatile analytes [17,18], and have been used to explore the hydrocarbon profile of live flies [7] as well as the metabolite distribution of a chili fruit [19].…”