I have 1cmx1cm TCPS samples and I only want to seed cells in the center (~0.3cm2 area). I have tried making PDMS rings and gluing it to the samples but there is always a leakage issue. If I do not use any thing and just put a drop of media in the center it is not very reliable. Is their a way (some water repellent pen etc.) that I can use to cover the edges of the sample? or some other method?
What work for my is the following.
You put a round cover slip, like this one: http://hansolsc.com/product/CSLIP20009/CSLIP20009_s.jpg into the dish and then but the cells and the media only to this round cover slip. Because of the surface tension the media is not flow up from the round cover slip when you handle it carefully - you can test it first without cells. Round cover slips are available in small size, so you have to search for such small ones try it with round cover slip from microscopy (should be in your institute) after sterilize them.
I have seen quite simple metod: fill the well of the plate with agarose, then cut out a new, smaller well in the middle of an agar. It was done with the cutter for cutting out rubber stoppers for glass vials (very old thing but made of metal and autoclaveable). If you use quite conentrated agarose, then cells will not migrate into it. And one more thing: agarose needs to be hot so it will attach tightly to the plastic.
@Sven Dittmann, Your method is valid but I have a different case here. I have cut TCPS plates to make 1cm*1cm sample and then I put these samples in well-plate and want to seed cells only on the samples (or in the center of the sample) so the method with coverslip is not valid here.
@Patrycja, the method you described is interesting (I used the same method to make PDMS rings actually). But as I ave surface topography on the TCPS samples and if I cover the whole samples with agarose and then cut out a smaller well in the middle, I'm not sure if all the agarose will be lifted out or there will be some thin layer of the agarose that will block the topography :(
OK, so it is more problematic. However, with the PDMS rings the main problem was that they were leaking as the plate has some specific architecture and the rings do not attach tightly enough, right? Have You tried to use some sealant, e.g., touch the bottom of the ring to the hot agarose and attach to the plate (or put the ring on a plate and add hot agarose all around it from outside so it would seal up the leakage) or smear the bottom of the ring with vaseline (it works well for the putting together chambers for a microinjection) to seal it up tightly to the plate, or even use nail varnish as a sealant?
I do not really remember, but maybe one can seal with some "hydrophobic" fat, glycerol or the pen, which exists for use without rings - but maybe it works with the rings.
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