Four 300 V DC power supplies (model ES 0300–045, Delta Elektronika B.V., Zierikzee, NL) were used to provide voltages to the sample plate, ion gun mosquito tip, and start and end of the stacked-ring ion guide, respectively. See Figure S1 of the Supporting Information for a scheme of the overall instrument and more details. See Figure 1 for a scheme and image of this ion guide and associated hardware. The technical merits and limitations of this instrument are also discussed.įor the modified source chamber, a custom, stacked-ring ion guide that allowed ion transmission from ions produced using both the stock timsTOF fleX laser and the added ion beam and also provided room for the MCP-based secondary electron detector (SED) was designed and manufactured in collaboration with Bruker Daltonik. Here, we demonstrate the multimodal capabilities of this instrument by analyzing biological tissue, generating SIMS, MALDI, and secondary electron (SE) images. This modification provides the benefits of multimodal SIMS and SE images in a top-of-the-line MALDI imaging mass spectrometer. Although not commercially available, such a modification could be applied to other timsTOF fleX instruments without disruption of existing MALDI workflows and using only commercially available software. This instrument uses the original timsTOF fleX standardized sample transfer modules, control, and data analysis software and is compatible with existing sample preparation. This instrument was made by integrating an Ionoptika 40 kV C 60 + ion gun into a prototype Bruker timsTOF fleX mass spectrometer using only a few custom components. In this manuscript we present a multimodal SIMS/MALDI instrument with secondary electron imaging capabilities. (6,7) Whereas SIMS produces, compared to MALDI, more elemental ions and fragments of larger biomolecules and usually has a smaller pixel size (usually between 50–2000 nm). (1) MALDI is useful for the analysis of intact biomolecules, but usually has a larger pixel size (usually between 5–50 μm). SIMS imaging is similar to MALDI-MSI, but uses an ion beam as a surface probe and generally does not require the addition of a matrix. These spatially resolved mass spectra can then be used to generate ion images of the surface. Each laser shot produces ions that are detected using a mass analyzer and converted into a mass spectrum. With MALDI-MSI, a photoactive matrix is applied onto the sample, after which a laser beam probes the surface. (1−5) Two of the most popular MSI techniques are matrix-assisted laser desorption and ionization (MALDI) and secondary ion mass spectrometry (SIMS). Mass spectrometry imaging (MSI) produces chemical images of a surface and is commonly used for biological and biomedical research. Furthermore, we characterize the performance of SIMS, SE, and MALDI imaging and compare the performance of the modified instrument to a commercial timsTOF fleX. We show multimodal images collected on this instrument that required only trivial registration and were acquired without sample transfer between imaging trials. In order to improve the efficiency of multimodal imaging and investigate complementary modes of MSI, we have modified a prototype Bruker timsTOF fleX by adding secondary ion mass spectrometry (SIMS) and secondary electron (SE) imaging capabilities while preserving the ability to perform matrix-assisted laser desorption/ionization (MALDI). These problems can be solved by using a single instrument that can image in multiple modes. Multimodal MSI images are often acquired using multiple MSI instruments, which leads to issues regarding image registration and increases the chance of sample damage or degradation during sample transfer. Multimodal imaging combines multiple imaging modes in order to get a more comprehensive view of a sample. Mass spectrometry imaging (MSI) is a surface analysis technique that produces chemical images and is commonly used for biological and biomedical research.
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