Matrix-assisted laser desorption/ionization-imaging mass methods

Matrix-assisted laser desorption/ionization-tandem mass spectrometric method (MALDI-MS/MS) has proven to be a reliable tool for direct measurement of the disposition of small molecules in animal tissue sections. As example, MALDI-MS/MS imaging system was employed for visualizing the spatial distribution of astemizole and its primary metabolite in rat brain tissues. Astemizole is a second-generation antihistamine, a block peripheral HI receptor, which was introduced to provide comparable therapeutic benefit but was withdrawn in most countries due to toxicity risks. Astemizole was observed to be heterogeneously distributed to most parts of brain tissue slices including cortex, hippocampus, hypothalamic, thalamus, and ventricle regions while its major metabolite, desmethylastemizole, was only found around ventricle sites. We have shown that astemizole alone is likely to be responsible for the central nervous system (CNS) side effects when its exposures became elevated. 

Thermogravimetric analysis Differential thermal analysis Differential scanning calorimetry Thermal volatiUszation analysis Evolved gas analysis Mass spectroscopy methods Matrix-assisted laser desorption/ionization Imaging chemiluminescence... 

In a separate study, a protocol for Matrix-assisted laser desorption-ionization (MALDI) imaging mass spectrometry (IMS) has been proposed.18 This IMS technique provides a new approach to visualize spatial distribution of thousands of molecular species, including peptides, proteins, and their metabolites in two- or three-dimensional levels. This approach may also provide a straightforward method of determining the tissue distribution of multiple peptides or proteins in a quantitative manner.18 Chu et al.19 reported a nondestructive molecular extraction method to obtain proteins from a single FFPE or frozen tissue section, without destroying the tissue morphology, such... 

Drexler D, Garrett T, Cantone J, Diters R, Mitroka J, Conaway M, Adams S, Yost R, Sanders M (2007) Utility of imaging mass spectrometry (IMS) by matrix-assisted laser desorption ionization (MALDI) on an ion trap mass spectrometer in the analysis of drugs and metabolites in biological tissue. J Pharmacol Toxicol Methods 55 279-288. doi 10.1016/j. vascn.2006.11.004... 

Traditional mass spectrometric imaging (MSI) methods, such as matrix-assisted laser desorption ionization (MALDI) and secondary ion mass spectrometry (SIMS), have become important tools for the investigation of molecular distributions in tissues due to their high ionization efficiencies and excellent lateral and depth resolutions. Invasive sample preparation and the need for vacuum conditions, however, are incompatible with the analysis of live samples. 

Matrix-assisted laser desorption ionization (M ALDI) has also been used for TLC/MS by Gusev et al. (61). Absolute detection limits of 2-4 ng were demonstrated for bradykinin, angiotensin, and enkephalin derivatives. Application of the MALDI support matrix to the TLC plate after separation is completed induces a planar diffusion of 1-1.5 mm. In an interesting application of the MALDI TLC/MS method, the mass spectra of ninhydrin-stained spots were obtained. Ions corresponding to the ninhydrin adducts with the sample molecules could be observed. A spatially resolved image for bradykinin on a TLC plate in a 2-(4-hydroxyphenylazo) benzoic acid matrix was also reported in this paper. 

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