WPI EVOM3, Инструкция по эксплуатации

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40 World Precision Instruments
APPENDIX D: 24 MM DIAMETER (6-WELL) INSERTS
Note that the resistance readings from 24 mm diameter tissue culture inserts (6-
well plates) obtained by using WPI’s STX series of electrodes will be 1.8 to 2.2 times
higher than that obtained using the
ENDOHM-24G
, because the
STX
electrode
cannot deliver a uniform current density over the relatively large membrane through
the small gap between the membrane and the bottom of the well. Therefore, the
resistance reading of a 24 mm (6-well) diameter insert obtained by STX electrodes
should not be used to calculate the unit area resistance. STX electrodes are only
intended for providing a qualitative measurement of cell monolayer health and
quantitative measurement of cell confluence. This is not a problem with smaller
inserts, such as the 12 mm and 6 mm diameter inserts, because of the relatively
smaller size of the membrane compared to the electrode. When the EVOM3 is used
with the EndOhm , it gives a repeatable and accurate value of membrane resistance
consistent with that obtained by using a well-designed Ussing chamber. It is also
consistent with that obtained by the STX electrode for the 12 mm and 6 mm diameter
filter inserts.
NOTE : The unit area resistance is independent of the area of the membrane and may
be used to compare data obtained from inserts of different sizes.
For 6-well plates (24 mm inserts), the
STX2-PLUS can be used to take readings at the
12 o’clock, 3 o’clock, 6 o’clok and 9 o’clock positions to look for low resistance points in
a 24 mm insert to test for confluence.
APPENDIX E: IMPROVING THE ACCURACY AND
REPEATABILITY OF THE SYSTEM
Whenever possible, operate the
EVOM3
meter with the battery charger disconnected.
This ensures maximum electrical isolation for the most accurate readings. When
the charger remains connected to the meter during measurements, electrical noise
can be introduced into the system. For the highest accuracy in measurement, WPI
recommends disconnecting the unit from the AC power source.
For 24-well or 12-well measurements the
STX2-PLUS
electrode is capable of making
precise measurements. The STX2-PLUS is designed primarily for 24-well inserts, and it
can be used with 24-well HTS plates* and 12-well inserts* with good results as long as
the placement is consistent. Consistent electrode placement and mechanical stability
are essential for consistent resistance results. Try to keep the fluid levels and fluid
temperatures constant. The use of a warming plate can add to measurement items
and reduce CO
2
out gassing during readings. CO
2
out gassing can change the pH of
the media and sharply increase a resistance reading. See "Tips and Advice" on page
6 and the notes on page 6.
*For 24-well HTS plates, keep the basal electrode centered in the basal access slot.
*For 12-well inserts, the
STX2-PLUS will have to be hand held.