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# How to calculate pg/ml/mg for tissue culture?

tissue culture dilutions

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### #1 murusa

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Posted 12 September 2013 - 12:41 AM

Hello!

I need an advice how to calculate final cytokine concentration in tissue culture in pg/ml/mg. I cultured tissue explants about 200mg per 700ul media. Then I collected supernatants and measured tnf production by ELISA (100ul of supernatant per well). My final result from this assay is in pg/ml but I need to calculate them with relation to mg of tissue.. How can I do that?

I tried to express my tissue culture concentration as 280mg/ml - but what I should do after that? Should I devide my ELISA result or multiply? A little bit confused..

### #2 bob1

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Posted 12 September 2013 - 01:18 AM

How I would do it is to calculate how much (total) cytokine was produced - i.e. take your concentration and multiply by the volume (keep units consitent, e.g. if you have pg/ml then the volume needs to be in ml...)

Then you have a total cytokine and you can work out how much was produced per mg tissue.  Units will not be pg/ml/mg, but pg/mg!

### #3 murusa

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Posted 12 September 2013 - 09:47 PM

you mean that:

if my elisa result for TNF-a is 200pg/ml, I should multiply this ammount = 200pg/ml x 0.7ml (culture well volume) = 140pg. And then I should devide it to 200mg ot tissue (tissue mass in a well) = 140pg / 200mg = 0.7pg/mg

am I right in my calculations? this way definitely correct to know how much was produced by mg..

I was just wondered about these units, because in papers with the measurment cytokines in tissues they put in their graphs "pg/ml/mg".. but if the way above is correct I could use it!

thank you again!

### #4 bob1

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Posted 13 September 2013 - 05:38 PM

I don't know how the papers do it - I don't work with cytokines, but in terms of science units like pg/ml/mg make no sense - think about it picograms per ml (of what) divided by mg of tissue?   The tissue mass and ml are unrelated and the volume is irrelevant other than as a normalizer to get the total cytokine production.

The way I suggested above is how I would do it, but if you followed your papers you would get 200 pg/ml/200 mg = 1 pg/ml/mg.

### #5 murusa

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Posted 15 September 2013 - 06:03 PM

thank you for your answer!! I think you are right.. I will calculate by your way! it is more reasonable..