Mass spectrometry imaging surface, tissue sections

Mass spectrometry imaging (MSI) circumvents these issues by combining MS with microscopy (5). Spatially resolved mass spectrometric experiments directly on the surface of tissue sections enable the reconstruction of images and therefore the localization of hundreds of molecules within their histological context without any labeling. MSI has therefore received considerable interest as an imaging technique for the ex vivo molecular interrogation of animal, human, or plant tissue sections (6). 

Two new independently developed techniques called Dart ° (direct analysis in real time) and Desi (desorption electrospray ionisation) are making a huge impact on mass spectrometry. Together they remove the need for sample preparation and vacuum, speed up analysis time and can work in the open air. The sample is held in a gas or liquid stream at room temperature and the impact induces the surface desorption of ions. The ions then continue into the vacuum interface of the MS for analysis. Samples can be hard, soft or even liquid in nature. Ifa et al. have used Desi to image biological samples in two dimensions, recording images of tissue sections and the relative concentrations of molecules therein. Jeol have launched a commercial Dart ion source for non-contact analysis of materials in open air under ambient conditions. 

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