Imaging of Biological Tissues by Desorption Electrospray Ionization Mass Spectrometry

Abstract

Mass spectrometry imaging (MSI) provides untargeted molecular information with the highest specificity and spatial resolution for investigating biological tissues at the hundreds to tens of microns scale. When performed under ambient conditions, sample pre-treatment becomes unnecessary, thus simplifying the protocol while maintaining the high quality of information obtained. Desorption electrospray ionization (DESI) is a spray-based ambient MSI technique that allows for the direct sampling of surfaces in the open air, even in vivo. When used with a softwarecontrolled sample stage, the sample is rastered underneath the DESI ionization probe, and through the time domain, m/z information is correlated with the chemical species' spatial distribution. The fidelity of the DESI-MSI output depends on the source orientation and positioning with respect to the sample surface and mass spectrometer inlet. Herein, we review how to prepare tissue sections for DESI imaging and additional experimental conditions that directly affect image quality. Specifically, we describe the protocol for the imaging of rat brain tissue sections by DESI-MSI. Video LinkThe video component of this article can be found at

Ambient analysis of leachable compounds from single‐use bioreactors with desorption electrospray ionization time‐of‐flight mass spectrometry

“…The surface distribution heterogeneity of BdtbPP could come from the un‐uniformity of TdtbPP degradation to BdtbPP upon gamma radiation of the film, which was used to sterilize the SUBs. The ability of DESI‐MS to probe the possible BdtbPP surface heterogeneity is not surprising as DESI‐MS has already been widely used in chemical imaging on various samples . However, an orthogonal approach would be desirable to confirm this heterogeneity of BdtbPP surface distribution suggested by the DESI‐MS analysis.…”

“…The ability of DESI-MS to probe the possible BdtbPP surface heterogeneity is not surprising as DESI-MS has already been widely used in chemical imaging on various samples. [33,34] However, an orthogonal approach would be desirable to confirm this heterogeneity of BdtbPP surface distribution suggested by the DESI-MS analysis. The relative low ion intensity of BdtbPP obtained with MeOH/CHCl 3 or MeOH solvent most likely comes from the limited dissolution and/or poor ionization efficiency of BdtbPP in these two solvents.…”

Review and perspectives on the applications of mass spectrometry imaging under ambient conditions

“…or slicing the native sample to generate tissue imprints on substrates, and (iv) drying the tissue sections immediately prior to analysis in a vacuum desiccator. 4,[25][26][27] 35 The enhanced performance is attributed to the intrinsic capability of the solvent to minimize redistribution and splashing of the analytes on the surface during MS analysis. Slower MS scan rates can improve spatial resolution as ions originating from one spot are scanned and removed from the mass analyzer prior to the sampling of the next spot on the surface.…”

“…microscope glass slides, filter paper, etc.) or slicing the native sample to generate tissue imprints on substrates, and (iv) drying the tissue sections immediately prior to analysis in a vacuum desiccator . The acquisition of MS data relies on the ion source (DESI, nano‐DESI, LAESI, etc.)…”

Ambient ionization mass spectrometric analysis of human surgical specimens to distinguish renal cell carcinoma from healthy renal tissue

“…Tumor and normal specimens (as determined by gross analysis performed in the pathology lab at IUSM) from each case were thaw mounted adjacent to each other on the same glass slide. A custom-built DESI source, similar to the DESI 2D Source available from Prosolia Inc. (Indianapolis, IN), was used to image the tissue (40). DESI spray solvent of dimethylformamide(DMF)-acetonitrile(ACN) 1:1 was used to minimize alteration of tissue morphology (33).…”