Ionization Sources and Mass Analyzers in MS Imaging

Abstract

Drug absorption, distribution, metabolism, excretion and toxicology study is one important step in drug discovery and development. MS imaging has become one of the popular methods in this field. Here, selected ionization methods such as matrix-assisted laser desorption/ionization, secondary ion MS and desorption electrospray ionization have been briefly discussed. To differentiate drug and drug metabolites from endogenous compounds present in the biological system, exact mass and/or tandem MS is necessary. As a result, mass analyzers such as time-of-flight, Fourier transform ion cyclotron resonance or Orbitrap are often the method of choice and are briefly introduced.

A Critical and Concise Review of Mass Spectrometry Applied to Imaging in Drug Discovery

“…The ionization method paired with any mass analyzer will significantly influence the sensitivity, spatial resolution, speed, and range of detected molecules. These have previously been reviewed in detail; 8,9 however, brief consideration will be given here to their utility in pharmaceutical R&D. Matrix-assisted laser desorption ionization (MALDI) allows spatially resolved detection of small and large intact molecules from surfaces and thin tissue sections. The technique requires the application of an ultraviolet (UV)-absorbing chemical matrix to the sample surface.…”

Decoding the Metabolome and Lipidome of Child Malnutrition by Mass Spectrometric Techniques: Present Status and Future Perspectives

“…Extraction methods for global metabolites and lipids have recently been extensively reviewed . Most MS-based metabolomics or lipidomics techniques utilize biological extracts except imaging MS, which utilizes tissue slices. , In this workflow, we suggest most commonly used biphasic (metabolite and lipid) extraction method following modified Folch methods (chloroform/methanol/water = 2:1:1) (Figure ) that our lab and others successfully utilized for diverse research in bioscience. ,, Quality control (QC) methods are critically needed for sample preparation, which include proper internal standards (isotopically labeled) to account for extraction variations and measurement of total protein concentration (cells and tissue samples), total DNA/RNA concentration (cell and tissue), wet/dry tissue weight, and fluid volume, which can be utilized for pre/postdata normalization . Sample specific observation such as body weight, height, and other factors can be considered for data normalization following data scaling or standardization tools such as autoscaling (mean-centered and divided by the standard deviation of each variable), pareto scaling (mean-centered and divided by the square root of the standard deviation of each variable), and so on …”

“…50 Most MS-based metabolomics or lipidomics techniques utilize biological extracts except imaging MS, which utilizes tissue slices. 61,62 In this workflow, we suggest most commonly used biphasic (metabolite and lipid) extraction method following modified Folch methods (chloroform/methanol/water = 2:1:1) (Figure 3) that our lab and others successfully utilized for diverse research in bioscience. 55,63,64 Quality control (QC) methods are critically needed for sample preparation, which include proper internal standards (isotopically labeled) to account for extraction variations and measurement of total protein concentration (cells and tissue samples), total DNA/RNA concentration (cell and tissue), wet/dry tissue weight, and fluid volume, which can be utilized for pre/postdata normalization.…”

Optimisation de la spectrométrie de masse par désorption/ionisation laser assistée par surface : la quête du Saint Graal basée sur l'étude des ions thermomètres.

“…These steps take place in the ion source of the mass spectrometer. There are many different ionization techniques [1]. For example, ions can be formed by electron bombardment (i.e.…”