Hi,
Currently, we are working on building potassium-sensitive microelectrodes for measuring voltage alterations in response to changes in the concentration of extracellular potassium.
However we are having trouble during the silanization step. We preheat a bottle containing around 20 ml of Dichlorodimethylsilane at 40 degrees Celsius. Then we place the capillaries on top and incubate for 70 minutes so that the vapors get into the sensor barrel (is there a way to check if this is actually working?). Afterwards, we transfer the capillaries to the oven for 2 hours at 200 degrees Celsius.
Do you have any tips to improve the silanization step for building K+-sensitive microelectrodes?
Thank you!
Alba
Hi,
Before silanization I clean the capillaries with acetone for 12 hours and rinse with abs. ethanol several times afterwards. Would that be enough for activating the glass prior to silanization?
Thank you for your help,
Alba
Wow, I recall doing this 30 years ago when I was making my own microelectrodes for both intracellular and extracellular measurements (We built our own super high impedance electrometers too as well as used commercial instruments, as funds allowed. Ah, those days in the Faraday cage make me nostalgic. Close the door or you will let the Faradays out?) Sorry, had a flashback... yes, as Tamás mentioned above, the surface prep of the glass used is critical to your success. The exact TYPE of glass is just as important too. Are you pulling your own tips or purchasing them? Try different types of glass formulations as well as different cleaning systems. We often acid washed ours before silanization. We also used a similar acetone bath as you described too (I do not recall which worked better). Many permutations of things to try.
To evaluate the results, do use an informal "dip in water test" and far more scientific electron spectroscopy method to gauge your coating results. You do not need much, just enough to get the fluid to stay intact as a clean slug inside the tube.
You should do this work under a dry nitrogen atmosphere. Your Dichlorodimethylsilane will rapidly react with atmospheric moisture to form polymer chains that will not become vapor at the temperatures you're using. Eventually you will end up with a gel of PDMS.
Plasma or Piranha or sodium hydroxide are the best surface preps for silanization. You need the hydroxyl groups to react with the silane.
Could you provide me more details about the protocol using sodium hydroxide treatment for surface activation prior to silanization?
Thank you!
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