Abstract
Brain imaging using time-of-flight secondary ion mass spectrometry (ToF-SIMS) has been reported to produce the distorted biomolecular distributions due to the cholesterol-induced matrix effect when cholesterol migrates to the surface, particularly in white matter, which contains a high level of cholesterol. Frozen-hydrated analysis has been used to inhibit the movement of cholesterol in the brain. In this paper, the authors propose new sample preparation and drying methods that can be used to obtain accurate biomolecular images at room temperature, instead of frozen-hydrated analysis using liquid-nitrogen, which must be continuously supplied to maintain the sample at -160 °C during the experiment. The rat brain prepared by the tape-supporting method on a precooled (-20 °C) stainless steel plate was freeze-dried in a load-lock chamber of ToF-SIMS for about an hour and moved directly to the main chamber. Using this preparation method, the authors found that cholesterol did not migrate to the surface in the corpus callosum (white matter) of the rat brain and sulfatide-related signals obtained from the cerebellum were not reduced in white matter. Our tape-supporting and freeze-drying sampling method for brain tissues could be a useful tool to study important metabolites of neurodegenerative diseases.
Highlights
Time-of-flight secondary ion mass spectrometry (ToFSIMS) has been widely used in biological tissue imaging owing to its high spatial resolution, molecular specificity, high reproducibility, and label-free characteristics, without the need for sample treatments
As a function of sampling and drying methods, we found that cholesterol migration to the brain tissue sample surface could be changed
In the white matter of the rat brain prepared by using the thaw-mounting method, cholesterol migrated to the sample surface regardless of room temperature-drying or freeze-drying
Summary
Time-of-flight secondary ion mass spectrometry (ToFSIMS) has been widely used in biological tissue imaging owing to its high spatial resolution, molecular specificity, high reproducibility, and label-free characteristics, without the need for sample treatments. Research using ToF-SIMS— with the aid of various cluster ion beams—has focused on biological applications such as characterization of the organic/bio-surface, mass spectrometric imaging of cells and tissues, disease diagnostics, and drug screening.. ToFSIMS imaging has been used for analyzing various tissues of the brain, eye, liver, kidney, bone, skin, and stomach.. 03B411-2 that it is possible to obtain accurate images of biomolecules on tissue by changing the sampling method. To obtain accurate molecular images from inhomogeneous and complex tissues such as the brain, the use of an appropriate sampling method is critical. This study was an attempt to understand the process of cholesterol migration in the rat brain tissue by improving the sample preparation method and drying process without any pretreatment
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