WPI STX4 Manuel utilisateur
WORLD
PRECISION
INSTRUMENTS
STX4
Electrode with Replaceable Blades
Compatible with EVOM Epithelial Volt/Ohm Meters
www.wpiinc.com
INSTRUCTION MANUAL
031122
STX4
World Precision Instruments i
Copyright © 2022 by World Precision Instruments. All rights reserved. No part of this publication may
be reproduced or translated into any language, in any form, without prior written permission of World
Precision Instruments, Inc.
CONTENTS
ABOUT THIS MANUAL ................................................................................................................... 1
INTRODUCTION .............................................................................................................................. 2
Features....................................................................................................................................... 2
Notes and Warnings................................................................................................................. 3
Parts List...................................................................................................................................... 4
Unpacking................................................................................................................................... 4
OPERATING INSTRUCTIONS......................................................................................................... 5
Positioning Electrode in a Culture Cup................................................................................ 5
Stable Repeatable Readings ............................................................................................. 5
Adjusting the Exposed Length of Electrode Blades ......................................................... 6
Preparing to Take Measurements ........................................................................................ 7
MAINTENANCE ................................................................................................................................ 9
Cleaning/Maintaining the STX4 Electrodes......................................................................... 9
Disinfecting the STX4 Electrodes........................................................................................... 9
Sterilizing the STX4 Electrodes .............................................................................................. 9
Storing the Electrodes ...........................................................................................................10
Replacing the Electrode Blades...........................................................................................11
Testing the STX4 Electrode...................................................................................................14
ACCESSORIES.................................................................................................................................17
TROUBLESHOOTING ...................................................................................................................18
APPENDIX A: KCL TESTING MIXTURES.....................................................................................20
APPENDIX B: COMPATIBLE INSERTS AND PLATES ...............................................................21
FREQUENTLY ASKED QUESTIONS............................................................................................23
WARRANTY .....................................................................................................................................27
Claims and Returns ................................................................................................................27
Repairs.......................................................................................................................................27
ii World Precision Instruments
STX4
World Precision Instruments 1
ABOUT THIS MANUAL
The following symbols are used in this guide:
This symbol indicates a CAUTION. Cautions warn against actions that can cause
damage to equipment. Please read these carefully.
This symbol indicates a WARNING. Warnings alert you to actions that can cause
personal injury or pose a physical threat. Please read these carefully.
NOTES and TIPS contain helpful information.
Fig. 1—The STX4 electrode is designed for use with the EVOM3 meter.
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INTRODUCTION
The STX4 electrode can be used with the EVOM3 and is designed to facilitate
measurements of voltage (potential dierence (PD)) and resistance (transepithleal
electrical resistance (TEER)) of cultured epithelia (cellular layer) grown on permeable
membranes in 12- and 24-well tissue culture plates. The STX4 can measure directly
inside the well plates with 12 and 24 inserts. STX4 is ideal for the 24-well transwell
format).
NOTE: These permeable membrane cell culture inserts are also commonly referred as
transwells.
Each STX4 electrode is made of two electrode blades, and each electrode blade
has an outer (current) and an inner (voltage) electrode. Current is applied between
two electrode blades, and resistance is measured by detecting the voltage change
between the inner electrodes of the electrode blades.
The STX4 is designed primarily for 24-well hanging inserts or transwells (for example,
Corning 3470). The STX4 can be used with 24-well high throughput screening (HTS)
plates (for example, Corning 3378) and 12-well inserts (for example, Corning 3460) with
good results, as long as the electrode placement is consistent. Consistent electrode
placement and mechanical stability are essential for consistent resistance results.
Use of a stable sample temperature and the same liquid volumes will result in better
reading stability and measurement consistency.
Features
• The STX4 electrode ts ideally onto 24-well hanging transwells and can stay hung
on top of these transwells (for hands-free operation). The electrode has improved
measurement precision since it mitigates or minimizes variabilities contributed by
electrode positioning seen with STX2 electrode.
Sensing region of electrode tips
Adjustment
Ring
Fig. 2—The electrode tips of the STX4 electrode have a metallic color and must be immersed
in the conductive liquid like a media or buer solution.
• The electrode tip (Fig. 2) is specially coated and does not need to be chlorided
with bleach or sodium hypochlorite for proper functioning, and it is not aected
by chloriding either. Chloriding was critical for the previous model (STX2-PLUS
electrodes) to maintain its functionality.
STX4
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• The electrode tip (active sensing area) of the STX4 is shorter than the STX2-PLUS
tip. Therefore, it requires less liquid volumes than the STX2-PLUS to keep the
electrode tips immersed and able to provide stable readouts.
• Electrode blades are replaceable. Over a period of use (for example, months or
years) when the electrodes may have formed deposits from media or samples
and may start showing reading instability, you may change the blades without
having to replace the entire electrode.
Notes and Warnings
CAUTION: Always lift the electrode by the body, never by the cable.
Fig. 3—(Left) Do NOT hold the electrode by the cable. It can physically break the internal
connections gradually.
Fig. 4—(Right) Hold the electrode by the plastic region indicated by the red arrow.
CAUTION: Limit the liquid immersion or liquid
spray level somewhere below the maximum level
indicated by the arrows in Fig. 5 (Right). You don’t
want the liquid to get inside and reach up to the cables
or connectors. You can wipe the rest of the electrode
with a paper towel sprayed with isopropanol or ethanol.
(Do not spray directly.)
Fig. 5—Don’t allow liquid to pass the line indicated by the arrows.
CAUTION: Make sure the blades of the electrode are not too deep that the
blades physically touch the membrane or the bottom of the well plate. The
blades should not be in direct physical contact with anything, aside from the
conductive liquid (media or buer) in which they are immersed.
Fig. 6—The inner electrode is positioned above the membrane without making contact.
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CAUTION: Do NOT apply any heat or ame to any portion of the electrode or
the electrode blades.
CAUTION: NEVER leave the electrode in alcohol (isopropanol or ethanol) for
more than 30 minutes at a time. Continuously soaking the electrode in alcohol
may weaken the protective coating on the electrode blades and can shorten
the electrode’s life. Electrode tips that show signs of peeling need to be replaced.
CAUTION: Do NOT use ammonia for cleaning.
CAUTION: Do NOT immerse the electrode head or any cable or connector
portion in liquid. Only the electrode tip portion can be immersed in liquid.
CAUTION: Do NOT sand or abrade the electrode surfaces. The electrode
blades (especially the tips) showing deep scratches need to be replaced.
Parts List
After unpacking, verify that there is no visible damage to the instrument. Verify that all
items are included:
(1) STX4 Electrode
(1) Pair of Spare Electrode Blades
(1) 99776 Wet Test Fixture
(1) Instruction Manual (available online at www.wpiinc.com/manuals)
Unpacking
Upon receipt of this instrument, make a thorough inspection of the contents and
check for possible damage. Missing cartons or obvious damage to cartons should be
noted on the delivery receipt before signing. Concealed damage should be reported
at once to the carrier and an inspection requested. Please read the section entitled
“Claims and Returns” on page 27 of this manual. Please contact WPI Customer
Service if any parts are missing at (941) 371-1003 or [email protected].
Returns: Do not return any goods to WPI without obtaining prior approval (RMA
# required) and instructions from WPI’s Returns Department. Goods returned
(unauthorized) by collect freight may be refused. If a return shipment is necessary,
use the original container, if possible. If the original container is not available, use a
suitable substitute that is rigid and of adequate size. Wrap the instrument in paper or
plastic surrounded with at least 100 mm (four inches) of shock absorbing material. For
further details, please read the section entitled “Claims and Returns” on page 27 of
this manual.
STX4
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OPERATING INSTRUCTIONS
Positioning Electrode in a Culture Cup
Proper placement of the electrode in the sample well is critical in making accurate
measurements. The STX4 electrode is designed to facilitate measurements of
membrane voltage and resistance of cultured epithelia in
tissue culture wells. The lengths of the electrodes are
unequal allowing the longer (external) electrode to go inside
the well of the well plate (basolateral) and the shorter one to
stay on top of the insert (apical).
Fig. 7— (Right) Electrodes in solution.
Stable Repeatable Readings
The STX4 is ideal for 24-well hanging inserts (for example,
Corning 3470). The electrode’s best performance can be
seen in this format. The STX4’s electrode design allows you
to set the correct depth and keep the electrode vertical
and centered on top of a 24-well transwell. Once the electrode is placed securely, and
the electrode movement ceases, a stable reading can be obtained with the EVOM3,
negating any need to take multiple measurements. Once the electrode’s working
depth has been set, use the same depth across all samples to compare results among
the sample set.
Ease of Use
The STX4 electrode design allows the electrode to hang vertically (Fig. 8, left) on top
of the 24-well hanging transwells and does not need to be handheld. Insert the outer
(longer) electrode into the basal access (well of the well plate) and the shorter one
on top of the membrane. Center the lower length adjustment ring onto the upper
edge of the insert and let the electrode stand on its own. The electrode blades no
longer need to be inserted at an angle (Fig. 8, center), eliminating any possibility of
introducing errors associated with angle variance during measurement. The STX4
electrode placement is stable and repeatable, as compared to the STX2 electrode.
*For 24-well HTS plates (for example Corning 3378), keep the basal electrode of the
STX4 centered in the basal access.
*For 12-well inserts, the STX4 electrode needs to be handheld.
STX4
Correct Placement
STX4
Angle Variance
STX4
Depth Variance
Fig. 8—The correct placement is on the left. An angle variance or depth variance could
change the measurements.
To the
EVOM3
STX4
Current-
passing
electrodes
(outer pair)
Membrane
Electrolyte
Gap
Voltage-measuring
electrodes (inner pair)
6 World Precision Instruments
Adjusting the Exposed Length of Electrode Blades
1. Firmly grasp the white adjustment ring at the end of the electrode body with one
hand. With the other hand, hold the shaft of the electrode body (Fig. 9). Rotate
the ring clockwise to extend the electrode blades so that they can enter deeper
into a sample. Rotate it counter-clockwise to retract the electrode blades so that
they can stay at a shallower depth inside a sample.
NOTE: Ideally, the ring should at least extend a little beyond the steel surface.
This allows the step in the ring to engage the outer edge of the insert (or the tri
supports of a hanging insert). Adjust the ring so that the sensing (coated) region of
the electrode blades (Fig. 10) stays fully immersed in liquid during measurement.
A change in depth can change readings. Once set, use this length adjustment
consistently to compare results in an experimental group.
Adjustment Ring
Sensing region of electrode tips
Fig. 9—Rotate the front ring to adjust the
exposed length of the electrode blades.
Fig. 10—The exposed electrode blade
lengths are properly adjusted. The arrows
highlight the coated sensing region.
2.
Align the electrode blades with the well inserts and position the
STX4
over the well
so that it rests securely in an upright position (Fig. 11, Fig. 12). (Images shown with
a Corning 3470 24-well insert and plate.) For greater stability, rest the cable on the
tabletop. For other plates and inserts, center the electrode blades, and the weight
of the top portion of the electrode will hold the electrode in place when taking a
measurement.
Fig. 11—The outer electrode reaches close to
the bottom of the well plate, and the inner
electrode does not touch the membrane.
Fig. 12—The STX4 sits securely over a 24-
well insert.
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