Stefan L. Luxembourg

Imaging mass spectrometry at cellular length scales

Imaging mass spectrometry (IMS) allows the direct investigation of both the identity and the spatial distribution of the molecular content directly in tissue sections, single cells and many other biological surfaces. In this protocol, we present the steps required to retrieve the molecular information from tissue sections using matrix-enhanced (ME) and metal-assisted (MetA) secondary ion mass spectrometry (SIMS) as well as matrix-assisted laser desorption/ionization (MALDI) IMS. These techniques require specific sample preparation steps directed at optimal signal intensity with minimal redistribution or modification of the sample analytes. After careful sample preparation, different IMS methods offer a unique discovery tool in, for example, the investigation of (i) drug transport and uptake, (ii) biological processing steps and (iii) biomarker distributions. To extract the relevant information from the huge datasets produced by IMS, new bioinformatics approaches have been developed. The duration of the protocol is highly dependent on sample size and technique used, but on average takes approximately 5 h.

Tools and strategies for visualization of large image data sets in high-resolution imaging mass spectrometry

Mass spectrometry based proteomics is one of the scientific domains in which experiments produce a large amount of data that need special environments to interpret the results. Without the use of suitable tools and strategies, the transformation of the large data sets into information is not easily achievable. Therefore, in the context of the virtual laboratory of enhanced science, software tools are developed to handle mass spectrometry data sets. Using different data processing strategies for visualization, it enables fast mass spectrometric imaging of large surfaces at high-spatial resolution and thus aids in the understanding of various diseases and disorders. This article describes how to optimize the handling and processing of the data sets, including the selection of the most optimal data formats and the use of parallel processing. It also describes the tools and solutions and their application in mass spectrometric imaging strategies, including new measurement principles, image enhancement, and image artifact suppression.

Imaging mass spectrometry using a delay-line detector

Microscope mode mass spectrometric imaging is crucially dependent on the availability of a high-resolution, position-resolved time-of-flight detector. Here, a new detection method for microscope mode imaging mass spectrometry is presented. A delay-line detector has been used for the first time as a position-sensitive detector in imaging mass spectrometry. The method is implemented on a matrix-assisted laser desorption/ionization time-of-flight (MALDI-ToF), as well as a secondary ion mass spectrometry time-of-flight (SIMS-ToF) instrument. Trypsinogen and bovine serum albumin samples have been used with a metal mask to determine the spatial resolution of the new detector using the MALDI-ToF instrument. The new detector set-up was successfully employed to generate mass resolved SIMS images from biological structures on the surface of thin tissue sections. The biological samples studied were taken from tumor grown from xenografted breast cancer cell lines and chicken embryonal sections.

High Resolution Mass Spectrometric Imaging of Cells and Tissue: MALDI and Surface Enhanced SIMS Put to Work

Molecular imaging techniques in the life sciences aim at the investigation of the relation between spatial organization and function of molecules in biological systems. The current rapid development of various mass spectrometric imaging technologies are a recognition of the power of mass spectrometry for biomolecular identification [1]. Mass spectrometry (MS) has transformed the way we look at macromolecular systems. Complex mixtures obtained from natural, biological or synthetic sources are now more or less routinely investigated with high resolution mass spectrometry. The unique specificity of mass spectrometry and its analytical sensitivity make it an ideal tool for the analysis of low-level biomolecules in complex multi-component mixtures. A biological surface like a tissue is a prime example of such a multi-component mixture. The rapid analysis of the local biomolecular composition with a high spatial resolution is one of the targets of biomolecular imaging MS.