Monday, April 26, 2021

IsoPlexis -- Targeted single cell proteomics panels! No mass spec required.


When I met with some applications scientists from this interesting little company, I told them that every time they referred to their instruments by the term "Iso" it made me involuntarily shudder.

Last year I was fortunate enough to lead a very small team of very smart people through a full multi-stage ISO17025 and then government audit process. There are exactly two ways to get multiple government bodies to bless Q Exactive assays. 

#1: Put this flowchart on your wall and live by it: 


#2) Put this exact same flowchart on your wall and use dry erase markers rather than more ...permanent... markers. (Why do I have so many pastel markers?) And live by it. 

Name aside -- what's an ISOPlexis or ISOSpark?  That link will take you to their very pretty website. They use thicker border lines on shapes than even I do. 

It's possible proof that I should shut up and listen more, because it is a surprisingly powerful platform for looking at proteins in single cells without needing to master a 2,000 pound instrument. 

What's it do? 

It uses little flow microchips to sort a small number of cells (you typically start with 30,000) by basically their normal propensity to migrate and flow around into little microchannels. An imager looks through and discards empty wells or wells where more than 1 cell ends up. It's pretty efficient with something like 800-1200 wells ending up with one cell in them. Blank? There is your background subtraction. More than 1 cell? Ignore. 

When the cells are stuck they're lysed (if the workflow is for what is inside the cell) and fluorescent antibody things are used to quantify the protein signal. 

What's the catch? Well, it's antibodies, so you've got their variability to consider. And you're obviously limited by the number of antibodies, dyes, fluorescent thingies, that you can use at once. 

However, they have panels that can quantify up to 32 proteins per cell! If your cells distributed well, 32 proteins per cell across maybe 1,000 cells? That could be very useful validation data. You can also work with them to build your own targets if they don't have a good panel for you. 

The instrument is less expensive than a mass spec (unless you're talking Advion Expression) but the chips aren't free, but they're WAY less expensive than doing 1,000 western blots, particularly if I have to do them (...which probably means 75,000 attempts....) 

ISOPlexis also realizes that we're out there (the ones with the half-ton machines) and they seem interested in bringing us all together. Last week they sponsored a really cool proteomics webinar with GenomeWeb where some great people from our side talked about where we are with our single cell -omics plans. I didn't find out about it until it was going on, but it's on demand here! This link might be glitchy because it's linked to my name, but I think it will get you there. 


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