Four unspecific spots in every well

[Questions from customers]

Hi Mabtech team,

 

Looking at the attached image, you can find 4 unspecific spots which are marked in red and appear in almost every well. As you can see, all of them are in the same position. This problem didn't happen in each plate, but most of the plates in the kit.  Do you have any idea what has happened?

//P

 

[Jens@mabtech.com]

Hi P,

 

I guess that you have been using a MSIP plate with a plastic underdrain? In that case, those 4 unspecific spots are impressions from the underdrain that has damaged the membrane of the well. This may happen if the underdrain has been pressed hard to the membrane at any time during handling, for example if too much force has been put into emptying liquid from the plate. In addition, did you use Tween-20 in the washing steps? You should not use Tween-20 as it permeabilizes the membrane making it more sensitive to damage. Tween-20 might be the reason why a slight damage caused by the plastic underdrain gave rise to such distinct unspecific spots.

 

The solution to the already developed plates is to manually neglect the 4 spots when counting. I know this might be tedious, but that is the only way. For future assays however, I have some tips. At approximately 1 minute into the following video we demonstrate the level of force you should use to remove liquid from plates:

 

The referred video shows our fluorescence enhancer reagent, but the same tip applies to any liquid that needs to be emptied from the plate: use the amount of liquid left on the paper towel as an indication of appropriate thoroughness.

 

For your knowledge, there are also other plates suitable for ELISpot that for example comes with detachable tray rather than an underdrain. Please visit our guide for more information on these different kind of plates: https://www.mabtech.com/knowledge-center/tutorials-and-guidelines/plate-coating-guide/plates-elispot-and-fluorospot.

 

Finally, you might be helped by watching our video on how to pre-treat ELISpot plates with ethanol. In this video you are introduced to the different plates available for ELISpot and how they should be handled:

 

Kind regards,

Jens

[Jens@mabtech.com]

Hi again P, 

Your are not alone in getting these unspecific spots, which is why we just uploaded a new tutorial video on how to optimally remove the underdrain and handle the plate. Feel free to check it out: