By Hugh Darrow
First published Neuroprosthetics Journal Quarterly (Fall 2010).
Prior to Darrow Industries' creation of PEDOT electrodes, almost all implanted neurostimulation devices on the market were based on the use of metal electrodes coming into contact with neural tissue. The better the contact, the more useful the device.
As an example, over 10,000 patients have had a deep brain electrode inserted into their skull to reduce tremors from Parkinson's disease. Since there are no pain neural fibres in the brain, the operation is performed while the patient is awake. When the electrode is inserted in the proper location, the tremors stop instantly.
Unfortunately, metal electrodes are stiffer than surrounding brain tissue, and also prone to the mechanical impacts encountered by the body. Thus, when implanted in tissue, they frequently produce inflammation and sheaths of glial tissue surrounding them, a situation which not only leads to tissue injury, but also reduces electrical effectiveness of the device.
PEDOT electrodes were a revolutionary improvement in that they relied on both conducting polymers and live neural cells in their design. The increased biocompatibility and electrical signal transduction properties of the conducting polymer electrodes addressed each of these issues and promised a new generation of implanted electrodes that would benefit patients and clinicians.