Scaling concentrations up for larger slides - (Oct/04/2012 )

Hi,

So I have been growing my cells on 13mm diameter circular slides (area 132mm^2)for confocal staining, and usually use stimuli at concentrations of 10ng/ml IL-1 or 10^7 bacteria, or whatever in 1ml media.

I am now doing a slightly different experiment which involves growing the same cells on a larger rectangular slide, 22mm*60mm (1320mm^2, coincidently almost exactly 10* the area of the circular slides) but growing them in 4ml media.

When I now add my stimuli, should I times the amount I add by 4 (to follow the new volume of media and get the same concentration) or by 10 (to follow the new surface area of the slides and thus keep the ratio of bacteria to cells the same).

I am currently keeping the concentration the same, but am getting results lower than I would have expected. Does anyone have any tips?

I would have said to keep the concentrations the same. It might be that you are coming across a cell density problem - if you are seeding 10x as many cells as before, but the well you have the coverslip in is not 10x as big, the cells will be more confluent and probably less susceptable to stimulation.