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Ba138 contamination

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twightman

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Posts: 17

Joined: Thu Oct 23, 2014 5:49 pm

Post Tue Feb 11, 2020 2:57 pm

Ba138 contamination

Hello everyone,
We have a group here wanting to run lung tissue on our CyTOF. These samples are already processed and cryopreserved. Some of these samples have Ba138 contamination and some don't. We have already narrowed down that these are coming from the actual samples and not the reagents being used. We are trying to figure out a cheap and easy way to screen these samples. Has anyone out there had similar issues and if so what kinds of screening processes have you put into place? Thank you so much in advance.
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mleipold

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Posts: 2086

Joined: Fri Nov 01, 2013 5:30 pm

Location: Stanford HIMC, CA, USA

Post Tue Feb 11, 2020 4:13 pm

Re: Ba138 contamination

Hi Terry,

A clarification question: at what point of the process are you wanting to screen the samples? And how much of each sample do you have?

If you have a decent amount of a sample (maybe an extra Million cells?), then you could try dissolving them in nitric acid and running them in solution mode for a couple minutes. If you see a streak at the right side of the Xe speckles, then the sample has Ba138. And you could even get hard numbers from a Solution Template, if you really wanted to.

Since Ba is so common, I'm not sure what you'd have to decide is your threshold cutoff. But since you'd probably be doing serial dilutions, there's probably a "step" in the series where the "good" samples are below X and the "bad" samples are above X.


Mike
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twightman

Participant

Posts: 17

Joined: Thu Oct 23, 2014 5:49 pm

Post Tue Feb 11, 2020 6:28 pm

Re: Ba138 contamination

Hi Mike,
What we plan on doing is taking a tiny bit of the cells and run them through before actually staining and running. Therefore the nitric acid sounds like a feasible plan. In what concentration do you usually use the nitric acid to dissolve them? How long of a incubation does that require? Would you need to wash the nitric acid out first? I'm sorry I just have never done this before.
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mleipold

Guru

Posts: 2086

Joined: Fri Nov 01, 2013 5:30 pm

Location: Stanford HIMC, CA, USA

Post Tue Feb 11, 2020 7:06 pm

Re: Ba138 contamination

Hi Terry,

Short answer: I'm not sure. Concentrated nitric would do the best job of dissolving everything down to components (ie, avoiding clumps and stuff). And since you're probably going to need to dilute 100-fold or more to be in a good measurement range, this would still drop your nitric concentration to <1% v/v (remember, Tuning solution is 2% v/v).

However, just using 2% nitric (or even Tuning solution) would probably be fine: if you start running either of those, residual material in the instrument goes from punctate "events" to streaks......at a minimum, this indicates that the metal is being released from the cells. Maybe 15-20min at 37C (probably longer than needed, but just to be sure).


If all you care about is the Ba138 signal, then Tuning solution might be a good way to go about it: you'd have the La139 signal and the other signals as references for intensity. Formally, this would be adjusted by whether Ba138 ionizes in the plasma as efficiently as the Lanthanides (it seems like it would be at least very close), but if you're just looking for fold-differences between "Good" and "Bad" Ba138 samples, it wouldn't matter since you'd be standardizing as "signal from the Ba138 content in 1M cells" or whatever.


Mike
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twightman

Participant

Posts: 17

Joined: Thu Oct 23, 2014 5:49 pm

Post Tue Feb 11, 2020 7:50 pm

Re: Ba138 contamination

Interesting. I will try out a couple different things and let you know how it goes. Thank you for your insight on this.
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MCOlivier

Contributor

Posts: 31

Joined: Mon Oct 05, 2015 9:48 am

Location: European Genomic Institute for Diabetes, Universitity of Lille, Institut Pasteur de Lille, France

Post Wed Feb 12, 2020 9:03 am

Re: Ba138 contamination

Hi all,

Trying to bring a little stone. We recently tested Gadolinium contamination in MRI Gadovist injected patients, and we were able to quantify Gado in cells "basically" by runing Ir stained cells and a concentration curve of solubilized Gado. In first atempt, we were very carefull at diluting cells a lot in order to avoid a potential deleterious saturation of the signal on the detector, but finally, we ran cells at 500 000/ml (cause Gado was not that much concentrated in our cells).
Maybe you could basically try this ;-)
Best
Olivier
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vrozot

Participant

Posts: 9

Joined: Fri Jan 31, 2014 12:52 pm

Post Thu Feb 27, 2020 6:28 am

Re: Ba138 contamination

Hi Terry,

If I had to bet the Barium comes from your samples and is patient dependant. Is there a way you can select samples based on clinical information. Smokers are likely to have high barium content in their lung cells, so running lung samples can become tricky. There is no way per se to clean samples as Barium would be integrated in DNA, the best is to dilute the maximum you can to not saturate the detector. We saw that the blacker our cell pellet is, the higher barium content you ll find.

Best,

Virginie

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