Hey guys

I have 20uL of a drug that has a stock concentration of 100ug/mL. I need to treat cells with this drug at different concentrations of 1ng/mL, 5ng/mL, 10ng/mL, 20ng/mL, and 50ng/mL. Each of these concentrations will be administered in two wells (each well has 200uL of media, so each concentration will need to be in around 500uL of media combined to be safe).

I do not know what is a suitable way to calculate a dilution so that it will be enough to use for each different concentration. And I'm not sure what is the amount of the drug that I use for each concentration.

Should the stock concentration be further diluted? if so, how will I do that?

Help will be much appreciated.