Electrode Encapsulation

The tight-cell layer is compromised when particulate matter is present on lead

Transcript

Typically, as I have eluded to, the tissue capsule surrounding the helically wound lead, of the Peterson electrode, appears as a thin, translucent structure at explants having been in place for months. This was not always the case though. Occasionally we observed a yellow-brown mass along the tract of the electrode, perhaps a few millimeters in length and sometimes several were noted along the lead. When the these structures were incised, under sterile condition and cultured for aerobic and anaerobic bacteria , the results came back negative. Polarized light microscopy sometimes reveled birefringent particles in the mass. This lead us to looks for particulate matter on the surface of the implant structure.

Shown on the left is a H&E stained section from one such yellow-brown mass. The cells were deemed inflammatory, mostly macrophages. Lead fabrication and handling can, potentially leave residue. Shown on the right is a scanning electron micrograph of a purposely contaminated lead that had been ultrasonically cleaned in Freon liquid for 10 minutes. These findings lead us to developing the cleaning procedure shown as a footnote to this vignette. The steps in the cleaning procedure that were later dropped, to eliminate the Freon from entering the atmosphere, are shown as text that has been crossed out.1

1Cleaning Protocol

All cleaning steps are to be carried out under the laminar flow hood. Personnel should wear clean room certified gloves in handling the electrodes and care should be taken to prevent electrode damage. The solvent to electrode ratio for each step should be on the order of 500 ml of solvent to 100 inches squared of electrode. Solvents should only be used once. Electrodes should be placed on clean room wipers as solvents are being changed.

1. Sonicate the electrodes in Freon TMS for 5 minutes.
2. Sonicate the electrodes in Safezone® (a Freon TF substitute) for 5 minutes.
3. Dip the electrodes in filtered distilled water1 (to eliminate static charge build-up from Freon).
4. Sonicate the electrodes in a 1:100 solution of Liquinox® in filtered distilled water1 for 5 minutes.
5. Sonicate the electrodes in filtered distilled water1 for 5 minutes.
6. Sonicate the electrodes in 95% ethanol for 5 minutes.
7. Sonicate the electrodes in ultrapure water2 for 5 minutes.
8. Allow the electrodes to dry on clean room wiper.

Cleaning Protocol (for 1st lamination)
1. The platinum foil should be cleaned following the protocol above. Note: The foil should be removed from the frame for cleaning and for lamination.
2. The silicone rubber sheeting should be cleaned following steps 4 through 8 of the protocol above.
3. The plates should be cleaned by wiping with ethyl alcohol if the cuff electrode is intended for an acute procedure, and according to the full cleaning protocol if the cuff electrode is intended for a chronic procedure.

Cleaning Protocol (for 2nd lamination)

1. The laminated electrode should be cleaned following steps 4 through 8of the cleaning protocol.
2. The silicone rubber sheeting should be cleaned following steps 4 through 8 of the cleaning protocol.
3. The plates should be cleaned by wiping with ethyl alcohol if the cuff electrode is intended for an acute procedure, and according to the full cleaning protocol if the cuff electrode is intended for a chronic procedure.

Final Cleaning Protocol (before packaging)

All cleaning steps are to be carried out under the laminar flow hood. Personnel should wear clean room certified gloves in handling the electrodes and care should be taken to prevent electrode damage. The solvent to electrode ratio for each step should be on the order of 500 ml of solvent to 100 inches squared of electrode. Solvents should only be used once. Electrodes should be placed on clean room wipers as solvents are being changed. Once the electrodes have been cleaned, they should not be removed from the laminar flow hood until they are packaged for sterilization.

1. Sonicate the electrodes in a 1:100 solution of Liquinox® in ultrapure2 water for 10 minutes with the heat function of the untrasonic cleaner turned on.
2. Rinse the electrodes 5 times in ultrapure water2.
3. Sonicate the electrodes in ultrapure water2 for 5 minutes.
4. Sonicate the silicone rubber cuffs in 95% ethanol for 5 minutes.
5. Rinse the silicone rubber cuffs with ultrapure water 5 times.
6. Sonicate the silicone rubber cuffs with ultrapure water for 5 minutes.
7. Allow the electrodes to dry on clean room wiper.
8. Package the electrodes for sterilization