problem with culturing on MEA chips

Hi! we've tried culturing mouse hippocampal neurons (E18) on both new and old glass MEA chips. All the chips were incubated overnightwith poly-D-lysine dissolved in borate buffer solution (5mg/ml) washed twice with sterile water and filled with plating medium (neurobasal medium + 10% FBS+ 1% P/S) for 1 day. the day after cells were cultured in that plating medium that was changed after 4 hours with culture medium (neurobasal medium + glutamax 1mM + B-27 50X +1%P/S). In both types of chips the problem was that the cells clump together instead of adhereing on MEA chips.
Why do we have that problem?what can we do to avoid clumping?
We know that plasma cleaning makes the surface more hydrophilic helping adhesion, but which one can we use? how often?
And now, how can we remove the cells and clean the chips?

Sorry for all the questions and thanks for help.

Simona

Dear Simona,

in our lab we use Harrick plasma cleaner. As the MEAs are used by several people I usually prefer to do the plasma treatment every time before I use the chips. (It takes just a minute).

Regarding the cleaning: We useTerg-A-Zyme from Sigma. Here you find a quick cleaning guide:
http://www.multichannelsystems.com/fileadmin/user_upload/Manuals/MEA-CleaningQuickGuide.pdf

Greetings

Thomas