Displaced dual‐mode imaging with desorption electrospray ionization for simultaneous mass spectrometry imaging in both polarities and with several scan modes

Abstract

Displaced dual-mode imaging (DDI) is introduced as a method for simultaneous imaging in positive and negative-ion mode on the same sample with desorption electrospray ionization imaging, as well as a method for simultaneous imaging in full-scan and tandem mass spectrometry (MS/MS) mode. DDI is performed by using a smaller row distance in the y-direction than the desired image resolution and recording for example every second row in positive-ion mode and the other half of the rows in negative-ion mode, thus resulting in two separate images. This causes some degree of oversampling, which is thus utilized to obtain complementary mass spectrometric of the sample. Imaging with both polarities is exemplified on an imprint of a Hypericum perforatum leaf containing secondary metabolites which ionize in both polarites and a mouse kidney containing phospholipids which ionize in positive or negative mode only. Simultaneous full-scan and MS/MS imaging was demonstrated on the same mouse kidney, as the mouse had been given a relatively low dose of the antidepressive drug amitriptyline. While the full-scan data allowed imaging of the endogenous phospholipids, the drug and its metabolites were only visible in the MS/MS images. The latter approach is useful, for example in whole-body imaging experiments where the full-scan data gives an overview of the tissue, and the MS/MS mode provides the sensitivity to image trace amounts of drugs and metabolites.

Polarity switching mass spectrometry imaging of healthy and cancerous hen ovarian tissue sections by infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI)

“…59–61 Due to limitations of MALDI MSI, some of which were mentioned above, polarity switching IR-MALDESI MSI of tissue sections at atmospheric pressure is of interest. As shown in Figure 1A, the IR-MALDESI polarity switching method was developed such that adjacent voxels are analyzed with opposite polarities.…”

“…Four modifiers (ammonium hydroxide, ammonium acetate, acetic acid, and TFE) were chosen based on literature review 61,62,64 , and added to the electrospray solvent (50:50 MeOH/H 2 O) at varying concentrations. The mouse liver tissue section was analyzed in quadrants, where each quadrant was imaged using a specific modifier (Fig.…”

High Resolution Tissue Imaging Using the Single-probe Mass Spectrometry under Ambient Conditions

“…Kidney samples have been the target of MS imaging experiments in the past in MALDI MS [35] and ambient MS imaging [20,36], where the contrast among the inner medulla, outer medulla, and the cortex make it an excellent target for MS imaging experiments (Figure 4a). The images were acquired at 10 μm/s raster speed with AGC mode on and were made with high mass resolution at 60,000 m/Δm.…”

Detection of Metastatic Breast and Thyroid Cancer in Lymph Nodes by Desorption Electrospray Ionization Mass Spectrometry Imaging

“…[1] In particular, cancer tissue diagnosis using ambient ionization MSI approaches has been explored by several research groups. [2] For instance, DESI-MSI, the most commonly used ambient ionization MS technique, has been employed to analyze several primary human cancer tissues including brain[3], prostate[4], gastric[5], kidney[6] and breast[7, 8]. Other ambient ionization MSI techniques such as laser ablation electrospray ionization mass spectrometry (LAESI-MS)[9], rapid evaporative ionization mass spectrometry (REIMS)[10], and nano-DESI[11] have been used to investigate the molecular signatures of biological samples and for cancer diagnosis.…”