Supporting Material: Telemetry method for monitoring of kidney oxygenation
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Supporting Material
Material and methods
Connection of the carbon paste electrode to a telemeter
These are the recommended procedures for attaching new carbon paste electrodes (CPE) to the
leads of the telemeter. The process of attachment of the electrodes to the telemeter leads requires 3
days and takes at least another 2 days before the connection is completely cured and ideal for
implantation.
Materials
 Fine forceps

Fine nose pliers

Scalpel

Needles for applying epoxy adhesive

FluoroEtch (Acton Technologies, Pittston, Pennsylvania)

Silver conductive epoxy adhesive (8331-14G, MG-Chemicals, Ontario, Canada).

Generic (slow setting) 2-part epoxy adhesive, Selleys Super Strength Araldite® (Selleys,
Australia & New Zealand)

Clear nail varnish

Polyurethane tubing (internal diameter of 1.5 mm).

Polytetrafluoroethylene (PTFE) coated silver wire (AG549511, Advent Research
Materials, Suffolk, UK).

CPE (Blue Box Sensors Limited, Dublin, Ireland).

Telemeter (TR57Y, Telemetry Research, Millar Instruments Inc, Houston Tx).
Electrode lead Preparation
The electrodes supplied by Blue Box Sensors are pre-etched by the supplier to enhance adhesion
between the polyurethane tubing (used to cover the connection) and the electrodes. Approximately
5 mm of the Teflon coating of the electrodes is removed at one end of the electrode to facilitate
insertion of the electrodes into the stretched stainless steel coils of the telemeter leads. A properly
etched electrode will have a light brown color on the Teflon coating. For best results we strongly
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recommend purchasing the electrodes from Blue Box Sensors, for use with the TR57Y telemeters.
Etching of the reference and auxiliary electrode needs to be done by the researcher him or herself.
Etching of the Reference and Auxiliary Electrodes (Fig. S1)
1. Cut ~ 5 cm and ~ 12 cm of the PTFE coated silver wire for the reference and auxiliary
electrode, respectively.
2. Heat FluoroEtch, vinegar and distilled water in a water bath at 80°C. FluoroEtch
deactivates rapidly once exposed to air. Therefore the sealed bottle should be placed inside
the water bath.
3. Immerse ~ 3 cm of the end of the electrodes to be etched into the etchant for 1 min before
immersing them into 70% ethanol and distilled water for 30 s each in succession.
4. Finally, immerse the electrodes into acetic acid (vinegar) for 1 min.
5. The etched end of the electrode will appear brown in color once it is successfully etched.
Preparation of the telemeter for reattachment of electrodes
The telemeters can be reused after they are explanted. Using a scalpel carefully remove the used
electrodes from the explanted telemeter, as close to the original join as possible to preserve as
much telemeter lead length as possible.
Lead Wire Preparation (Fig. S2)
1. Place the telemeter leads on a flat surface so that the tubing is not stretched and cut off any
used and exposed stainless steel coiled wire.
2. Cut the leads so that all three of the telemeter leads are of the same length.
3. For each lead, hold the polyurethane tubing upright and using a pair of long nose pliers,
extend and stretch the unexposed stainless steel coiled wire ~ 1 cm past the end of the
polyurethane tube.
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4. Carefully remove any colored silicone (blue, black or red coverings around the coiled
wires) from within the center of the extended coiled wire by using forceps or by rolling the
silicone coverings on the lead in between two fingers
5. Cut the stretched lead wire so that approximately 3 mm is extending out of the end of the
tubing for each lead.
6. The leads are color coded as follows:

Blue Lead = CPE

Black Lead = Reference Electrode

Red Lead = Auxiliary Electrode
Electrode Attachment
1. Insert the exposed wire of the electrode into the coiled telemeter lead wire (at least 2 mm)
(Fig. S2).
2. Mix a small amount of the 2 component silver conductive epoxy (1:1 ratio). The working
time of this product is about 10 min. After that time it gets too thick to apply. Using a
needle apply the silver epoxy in between and around the areas where the electrode comes
into contact with the telemeter leads (Fig. S3). Ensure that the silicone tubing of the
electrode is free of silver epoxy.
3. Using a fresh (or cleaned) needle remove excess epoxy. The join needs to be able to fit
inside the polyurethane tubing, so the connection should be no wider than the coiled wire
itself as shown in Fig. S3.
4. Leave the silver epoxy to dry overnight.
Sealing the Connection
1. Coat the silver conductive epoxy with 2 layers (30 min in between each) of clear lacquer
(nail varnish).
2. After the second coating is dry (>30 min), mix a small amount of the 2 component
adhesive epoxy in a 1:1 ratio.
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3. Apply a layer of adhesive epoxy over the silver epoxy layer. Cut a piece of polyurethane
tubing (1.5 mm inner diameter) and carefully slide it along the electrode, ensuring that the
tubing covers the connection and fits around the telemeter lead (Fig. S4). Take care not to
damage the tip of the carbon paste electrode.
4. Leave this to dry overnight. Keep the leads and electrodes vertical to prevent uneven
setting of the glue (Figure S5).
5. Mix a small amount of the 2 component adhesive epoxy in a 1:1 ratio. Allow it to cure for
5 minutes before applying to the connection.
6. Apply the epoxy adhesive to each of the connections so that all sides are covered and that
some of the etched (brown) part of the electrode coating is covered. Do not apply excess
epoxy or it will run down the electrode. Ensure that both ends of the polyurethane tubing
covering the silver conductive epoxy layer are completely sealed as in Figure S5.
7. Leave to dry/cure for a minimum of 2 days. Once the epoxy adhesive is completely dry,
the electrodes can be prepared for implantation.
Preparation of electrode for implantation in the kidney
Before the electrodes can be implanted, a length of the insulating Teflon coating of the auxiliary
and reference electrode has to be removed. For the reference and auxiliary electrode, remove ~ 5
mm and 8 cm of the Teflon coat respectively, by rolling a scalpel gently along the Teflon coated
silver wire, ensuring you do not damage the exposed silver wire in the process (Fig. S6).
As renal tissue oxygenation is spatially heterogeneous, the depth of electrode implantation will
affect the measured oxygen concentration. For cortical implantation, it is recommended that you
bend the tip of both the carbon paste and reference electrode at a 90° angle, ~ 2 mm from the
electrode tip. For inner medullary implantation, it is recommended that you bend both the carbon
paste and reference electrode at a 90° angle ~ 5 mm from the electrode tip.
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Sterilization
The effects of ethylene oxide gas sterilization on the carbon paste electrodes have not been
determined. We currently recommend that the radio transmitter of the telemeter and the lead
wires, but not the attached electrodes, are cold sterilized using 2% glutaraldehyde. At the time of
surgery, the surface of the electrodes, with the exception of the carbon paste electrode, can be
sterilized using 70% alcohol. DO NOT wipe the tip of the carbon paste electrode as this will ruin
the carbon paste which is the absolutely necessary for the functioning of the oxygen telemeter.
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Fig. S1 Etching the reference and auxiliary electrodes to enhance adhesion between the
polyurethane tubing (used to cover the connection) and the electrodes.
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Fig. S2 Preparation of the telemeter lead wires. The stainless steel coiled wire is stretched until it
extends 3 mm past the polyurethane tube. All three electrodes are placed within the stretched
stainless steel coiled wire.
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Fig. S3 Application of the silver conductive epoxy. The silver conductive epoxy is applied on the
area where the exposed wire of the electrodes makes contact with the coiled stainless steel wire of
the telemeter lead.
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Fig. S4 Application of the first layer of epoxy adhesive. After applying the epoxy adhesive on the
connection, precut polyurethane tubing is put over it to increase the strength of the connection.
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Fig. S5 Application of the second layer of epoxy adhesive. After the first layer has dried overnight
(photo bottom left) a second coat of epoxy adhesive is applied. The result is shown in the bottom
photo on the right.
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Fig. S6 Preparing electrodes for implantation in the kidney. After stripping Teflon of auxillary and
reference electrodes the CPE and reference electrode are bent at a 90° angle, 5 mm from the electrode
tip and the auxiliary electrode is coiled (10 mm diameter).