Re-using unloaded agarose gel - (May/24/2010 )

Hello,
I am wondering if i can use unloaded wells in 2.5% agarose in another run given that the gel has been used only in one run and kept soaked in TAE at room temp for 8hrs. would it be okey if the gel has been used again....?

I sometimes reuse gel that has unloaded wells, but it may depend on how long the previous run was. Ethidium bromide travels across the gel in direction opposite to DNA, so if you ran your gel for a long time it may be out of the gel already.
Also I run the gel the same day so I don't have experience with a prolonged storage at RT. If I want to use one gel for two times without compromising quality, I cut it before run and store the unused half in running buffer in a fridge.

Basically, if you value your samples you should make a new gel. I'm only doing it when I just need to check someting easily reproducible.

If you don't care about DNA cross-contamination, it is quite possible to heat used agarose gels and recast them for reuse.

phage434 on May 24 2010, 08:35 AM said:

You don't really even need to recast. I know one lab that reused gels to save money. You really only want to reuse gels for visualizing digests or such, not purifying of course but they would just run the gel for extended periods of time at a low voltage (to prevent the gel from getting too warm) and would run all DNA out from the first sample and then would just reload and rerun. They stored the gels in TAE in the fridge after purging the sample so they always had gels ready to grab and load.

I do it all the time, though may not be good lab practice. I store them in TBE and they're all right for several days. Again if you're running samples just to check that they're there or not it's all right, but if you're doing it to determine size and everything I'd go for a new gel. Mind you I post stain my gels with EtBr so I just restain them after I've ran my gels. Hope that helps.

phage434 on May 24 2010, 10:35 PM said:

This is what I do too, i remelt in microwave, re-add ethidium bromide and recast them.
Used up to 20 times and don't have much issue...it just looks dirty.
After all I use it to see whether there is band or no band so this will not be a problem for me.

You can just add some EtBr in the bottom end of the tank and either load unused wells, or previously used wells, if the product was run long enough.