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CAS vs CAS Plus: Can regular CAS be used on the CyTOF XT?

PostPosted: Thu Feb 10, 2022 1:05 pm
by thinkCara
Hi All,

We are now the proud owners of a CyTOF XT and slowly figuring out that there is a new cell acquisition solution (CAS) and new beads (SKU 201245) for the XT.
Does anyone know if regular/old CAS (SKU 201241) works with CyTOF XT or do we have to switch to the new CAS Plus (SKU 201244)?
Has anyone tried using regular CAS on the XT?
What's the difference between the CAS formulations?
My limited google searches haven't returned anything useful thus far.


Re: CAS vs CAS Plus: Can regular CAS be used on the CyTOF XT

PostPosted: Thu Feb 10, 2022 2:05 pm
by oAMIRo
Congrats on the XT!

I've been told CASplus prevents the increase in the negative signal observed particularly on long run time.
I got it a couple of weeks ago but haven't had the chance to tested it yet...


Re: CAS vs CAS Plus: Can regular CAS be used on the CyTOF XT

PostPosted: Thu Feb 10, 2022 4:05 pm
by mleipold
Hi Cara and Amir,

Short answer: Fluidigm will not tell us what the difference is.

Back in July 2021 when the XT launched, I asked, and got the following response:

Q: "How is CyTOFXT CAS different from Helios CAS? Both SDS list Amm nitrate <0.1%. What happens if you use Helios CAS?"
A: "CAS Plus is buffered and is optimized for long acquisitions that are enabled by XT (up to 23 hours)."

Based on that statement, it appears that there's some kind of buffer. Exactly what the buffer is, no idea: it can't be an inorganic salt like phosphate, as that would build up on the injector and would have to be some burnable (maybe HEPES?). But it has to be rather low in concentration, or it should be required to be listed on the MSDS......

Similarly, it appears that they're still using ammonium nitrate, rather than switching to something else ( eg thread here: viewtopic.php?f=1&t=1405&p=3986&hilit=bicarbonate#p3986 )

You might be able to get more info out of Fluidigm if you contact your FAS directly and have specific, assay-important questions. Kinda like how many companies don't list their buffer components, but if you contact them and say "hey, does it contain X? I want to use your product, but X interferes with my experiment and I can't use it if it does", you can often at least get a "yes/no" answer.