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zhangxu04's picture

hi everyone:

I try to firepolish my pipette.

it is very easy and fast to get G seal after firepolish.

but when break cell membrane to establish whole cell mode, I found It is not stable, down to about 200 M ohm and a very significant leak current

could anybody give me some suggestion

neuro's picture
we never firepolish, and

we never firepolish, and getting a gigaseal has never been a problem.  (pyramidal neurons, hippocampal neurons, purkinje cells (in slices, in vivo, or in culture) and hek293 cells.  we use 1.5 mm OD thick wall borosilicate glass, 4-5 mohm resistance.  apply about 0.2 ml of pressure and dimple the cell, withdraw the pressure and the resulting suction should be enough to form a gigaseal.  if not, give a little more suction, but not much.  i break the membrane slowly with additional suction after the gigaseal has former.  don't wait too long after you get a giga seal to break the membrane (otherwise you pull too much membrane up into the pipette).