Macademics: Mass Spectrometry Imaging

Hey Everyone! It's my favorite time of the month, #Macademics! This month I'm going teach you all a little bit about how people use mass spectrometry for imaging biological samples. 

This is hands down my favorite application to mass spect. Everyone in my group knows how cool I think this is and how mad I am that we don't do it, but since I'm starting to analyze tissue samples myself I thought this was an appropriate topic this month. 

First things first, mass spectrometry imaging (MSI) is a technique that's used to visualize where molecules are spatially on a sample. You can look at biomarkers, proteins, etc. by their mass-to-charge ratios. (Remember, that's what mass spect measures). As you can see from the picture above, each ion of interest is a denoted by a certain color and you can compare the colored to non-colored sections of the tissues to understand where there's a high concentration of each. Typically, there's a correlation to where certain ions are in the tissue sample to a particular disease, but I won't go further into the biochemistry of this application. 

When sampling a tissue sample, being able to ionize the compounds of interest are important, so for MSI, laser-based techniques are used. One of the most common is MALDI, or matrix-assisted laser desorption and ionization. In general with MALDI, you would coat the tissue sample with a matrix that can absorbs laser radiation, which then helps to charge the markers you're looking for. In order to image, you have to irradiate one region of the tissue at a time. You'd collect a spectrum in one spot and then make your way through the rest of the sample. To get the spatial distribution plots, you'd use the software. You can pick a single peak and the software maps out all of the regions where that peak showed up in the shape of your sample. Pretty cool right? 

So what do people use this for? Well typically it's used to image human and animal tissue samples for applications in understanding diseases, diagnostics, and even drug delivery. You can use it for cancer research, neuroscience studies, anything with some sort of biological relevance really. 

I hope you learned a little bit about my favorite mass spec application. Our last posts of the year are coming out next week so be on the lookout. 

-The Chemist 


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